CN-122026491-A - Improved SEPIC converter for broadband oscillation suppression of distribution network and control method

CN122026491ACN 122026491 ACN122026491 ACN 122026491ACN-122026491-A

Abstract

The invention discloses a distribution network broadband oscillation suppression type improved SEPIC converter and a control method, which belong to the technical field of converters and comprise an energy input end, an improved SEPIC converter, a broadband oscillation suppression network, a full-bridge inverter, an LC low-pass filter, a load and a control system, wherein the energy input end is a solar photovoltaic module array and used for providing initial direct-current electric energy, the improved SEPIC converter is connected to the energy input end and used for boosting the input direct-current voltage to target voltage, the broadband oscillation suppression network is connected to the output end of the improved SEPIC converter and used for detecting and suppressing broadband oscillation, the full-bridge inverter inverts the direct-current voltage output by the improved SEPIC converter into alternating-current voltage, the LC low-pass filter is connected between the output end of the full-bridge inverter and a load and a power grid and used for filtering high-frequency switching harmonic waves in the output voltage of the full-bridge inverter and smoothing output voltage waveforms, the load is a final energy output object, and the control system is responsible for monitoring, calculation and control instruction generation of the whole system. The alternating voltage THD output by the invention is effectively reduced.

Inventors

YOU XINYU
SHI TONG
XIONG NAN
WU PENG
YIN CHENBIN
WANG ZHUOYUE
Dai jiyulei
WANG YANG
SONG ZIHONG
HE MINGJUN
CAI YONGXIANG
XU YUTAO
YANG LUNHUI
ZHOU ZIJIAN
ZHANG SONG

Assignees

贵州电网有限责任公司

Dates

Publication Date: 20260512
Application Date: 20251226

Claims (10)

1. The improved SEPIC converter is characterized by comprising an energy input end, an improved SEPIC converter, a broadband oscillation suppression network, a full-bridge inverter, an LC low-pass filter, a load and a control system; the energy input end is a solar photovoltaic module array and is used for providing initial direct current electric energy; The improved SEPIC converter is connected to an energy input end and is used for boosting an input direct-current voltage to a target voltage, and comprises a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor, a third capacitor, a first diode, a second diode, a third diode, a fourth diode, a fifth switching tube and a broadband oscillation suppression network; The broadband oscillation suppression network is connected to the output end of the improved SEPIC converter and is used for detecting and suppressing broadband oscillation and comprises a broadband damping resistor, a broadband damping capacitor and a multi-band resonance suppression circuit; The full-bridge inverter inverts direct-current voltage output by the improved SEPIC converter into alternating-current voltage and comprises a first switching tube, a second switching tube, a third switching tube and a fourth switching tube; The LC low-pass filter is connected between the output end of the full-bridge inverter and the load and the power grid, and is used for filtering high-frequency switching harmonic waves in the output voltage of the full-bridge inverter and smoothing the output voltage waveform, and comprises a fourth inductor and a fourth capacitor; The load is a final energy output object; the control system is respectively connected with the energy input end, the improved SEPIC converter, the full-bridge inverter, the LC low-pass filter and the load and is responsible for monitoring, calculating and control instruction generation of the whole system.
2. The improved SEPIC converter of claim 1, wherein the improved SEPIC converter comprises an operation mode 1 and an operation mode 2; the working mode 1 comprises that a fifth switch tube is conducted, a first diode and a second diode are forward biased, a third diode, a fourth diode and a fifth diode are reverse biased, input voltage is respectively applied to a first inductor and a second inductor, the first inductor is charged through the first diode, the second inductor is charged through the second diode, and a second capacitor and a third capacitor charge the third inductor through the fifth switch tube.
3. The broadband oscillation suppression type improved SEPIC converter of the distribution network of claim 2, wherein the working mode 2 comprises the turning-off of a fifth switching tube, the forward biasing of a third diode, a fourth diode and a fifth diode, the reverse biasing of the first diode and the second diode, the common superposition of an input voltage, energy on the first inductor and the second inductor and voltage on the second capacitor, the transmission of energy to a full-bridge inverter terminal through the fifth diode, the transmission of energy stored in a third inductor to the full-bridge inverter terminal through the fifth diode, and the common charging of the third capacitor by the input voltage, the first inductor and the second inductor through the third diode and the fourth diode.
4. The improved SEPIC converter for broadband oscillation suppression of a distribution network according to claim 3, wherein the broadband oscillation suppression network comprises an RC network formed by a broadband damping resistor and a broadband damping capacitor and a multiband resonance suppression circuit, the RC network mainly provides damping for high-frequency oscillation, and the multiband resonance suppression circuit provides impedance characteristics for oscillation of a specific frequency band through a plurality of groups of LC series resonance branches, so that the selective suppression for oscillation of different frequency bands is realized; When broadband oscillation occurs, the oscillation energy is consumed by the broadband damping resistor, and meanwhile, the multi-band resonance damping circuit provides a low-impedance path in a specific frequency band, so that the oscillation energy is guided to the damping circuit to damp the oscillation.
5. The broadband oscillation suppression type improved SEPIC converter of the distribution network of claim 4, wherein the multi-band resonance suppression circuit comprises n resonance inductors and n resonance capacitors; The n resonant inductors are respectively a first resonant inductor, a second resonant inductor and an nth resonant inductor, the n resonant capacitors are respectively a first resonant capacitor, a second resonant capacitor and an nth resonant capacitor, and each group of resonant inductors and resonant capacitors are connected in series to form a resonant branch aiming at a specific frequency band.
6. The improved SEPIC converter with broadband oscillation suppression of a distribution network as claimed in claim 5, wherein the control system comprises a first A/D module, a second A/D module, a first driving circuit, a second driving circuit, a disturbance observation algorithm module, a sinusoidal modulation module, a PWM generation module, a broadband oscillation detection module, a multiband PR control module, a fundamental frequency PWM control module and an adaptive parameter optimization module; the first A/D module is used for collecting analog signals of photovoltaic input voltage and input current and converting the analog signals into digital signals; The second A/D module is used for collecting voltage signals and current signal analog signals output by the system and converting the voltage signals and the current signal analog signals into digital signals; The first driving circuit is used for driving the fifth switching tube; The second driving circuit is used for driving a first switching tube, a second switching tube, a third switching tube and a fourth switching tube of the full-bridge inverter.
7. The improved SEPIC converter with broadband oscillation suppression of distribution network as claimed in claim 6, wherein the disturbance observation algorithm module is used for executing a maximum power point tracking algorithm and calculating a target reference value required for realizing maximum power output; the sine modulation module modulates the maximum power point tracking result output by the disturbance observation algorithm module into a sine wave reference signal; The PWM generation module receives the sine reference signal output by the sine modulation module and compares the sine reference signal with the high-frequency carrier signal to generate a pulse width modulation signal for driving the main switch tube of the improved SEPIC converter; the broadband oscillation detection module monitors broadband oscillation in the system in real time through a time-frequency analysis method, and extracts frequency and amplitude characteristic information of the oscillation; The multi-frequency-band PR control module is used for comparing the acquired output voltage signals and current signals with a given standard sine wave synchronous with a power grid, calculating a control error, accurately tracking fundamental frequency sine signals and providing inhibition for the detected broadband oscillation frequency band; the fundamental frequency PWM control module receives the modulation signals output by the multi-band PR control module and generates PWM signals for driving four switching tubes of the full-bridge inverter; the self-adaptive parameter optimization module dynamically adjusts parameters of the multi-frequency PR control module and parameters of the broadband oscillation suppression network according to oscillation characteristic information provided by the broadband oscillation detection module, and realizes self-adaptive suppression of oscillation of different frequency bands.
8. A control method of a distribution network broadband oscillation suppression type improved SEPIC converter, applying the distribution network broadband oscillation suppression type improved SEPIC converter according to any one of claims 1 to 7, characterized by comprising: the first A/D module collects voltage signals and current signals of the input end of the main circuit, and outputs digital signals after A/D conversion; The disturbance observation algorithm module receives the digital signal output by the first A/D module, executes a maximum power point tracking algorithm, calculates a target reference value required for realizing maximum power output and outputs a control signal; The sine modulation module receives the control signal output by the disturbance observation algorithm module, modulates the tracking result of the maximum power point into a sine wave reference signal and outputs a modulation signal; The PWM generation module receives the modulation signal output by the sinusoidal modulation module, and generates a pulse width modulation signal for driving the main switch tube of the improved SEPIC converter by comparing the sinusoidal reference with the carrier wave; the first driving circuit receives the PWM signal output by the PWM generating module, outputs a control signal to the fifth switching tube and controls the switching and the conduction of the fifth switching tube; The second A/D module collects voltage signals and current signals of the output end of the main circuit, and outputs digital signals after A/D conversion; The broadband oscillation detection module receives the digital signal output by the second A/D module, monitors broadband oscillation in the system in real time through a time-frequency analysis method, and extracts frequency and amplitude characteristic information of the oscillation; the self-adaptive parameter optimization module receives the oscillation characteristic information provided by the broadband oscillation detection module, and dynamically adjusts parameters of the multi-band PR control module and parameters of the broadband oscillation suppression network; The multi-frequency-band PR control module receives the digital signal output by the second A/D module, compares the acquired output voltage signal and current signal with a given standard sine wave synchronous with a power grid, calculates a control error, accurately tracks a fundamental frequency sine signal, provides inhibition for a detected broadband oscillation frequency band, and calculates a modulation signal required by an inverter; The fundamental frequency PWM control module receives the modulation signals output by the multi-band PR control module and generates PWM signals for driving four switching tubes of the full-bridge inverter; The second driving circuit receives PWM signals output by the fundamental frequency PWM control module, outputs control signals to the first switching tube, the second switching tube, the third switching tube and the fourth switching tube respectively, and controls the switching and the conduction of the four switching tubes.
9. The method for controlling a broadband oscillation suppression type improved SEPIC converter of a distribution network as claimed in claim 7, wherein the method for monitoring the broadband oscillation in the system in real time by a time-frequency analysis method comprises, And carrying out frequency spectrum analysis on the voltage signal and the current signal output by the system, identifying oscillation components exceeding a preset threshold value, and extracting the frequency and the amplitude of the oscillation components as oscillation characteristic information.
10. The method for controlling a broadband oscillation suppression type improved SEPIC converter of a distribution network as claimed in claim 8, wherein the adaptive parameter optimization module receives the oscillation characteristic information provided by the broadband oscillation detection module, dynamically adjusts parameters of the multiband PR control module and parameters of the broadband oscillation suppression network, and comprises, And adjusting the resonance gain of each frequency band in the multi-frequency band PR control module and adjusting parameters of an RC network and a multi-frequency band resonance suppression circuit in the broadband oscillation suppression network.

Description

Improved SEPIC converter for broadband oscillation suppression of distribution network and control method Technical Field The invention relates to the technical field of converters, in particular to an improved SEPIC converter with broadband oscillation suppression of a distribution network and a control method. Background Solar photovoltaic power generation is widely used as a clean energy conversion mode. A typical photovoltaic system generally includes a photovoltaic array, a DC-DC converter, an inverter, and a maximum power point tracking controller. In order to improve the voltage gain, various DC-DC converter topologies are used in the prior art, such as multi-level converters, interleaved boost converters, voltage multipliers, coupled inductor converters, switched capacitor converters, and resonant converters. Maximum power point tracking techniques are used to maximize the energy output of the photovoltaic module in order to optimize the energy capture efficiency of the photovoltaic module to operate at the maximum power output point. For grid-tied or independently operated photovoltaic systems, the inverter converts direct current to alternating current. In terms of control strategies, PWM modulation techniques are commonly used and leakage current issues need to be considered in grid-connected systems, especially in transformerless topologies. Meanwhile, the high-proportion new energy and the power electronic equipment are connected, so that the running mode and the dynamic characteristic of the power system are obviously changed, and the dynamic behavior of the power system is more complex and changeable. In the novel power distribution network, power electronic equipment is connected with a network through power electronic equipment, the network connection characteristic relates to coordination and cooperation of a plurality of control loops, the control bandwidth spans a plurality of orders of magnitude, and the broadband characteristic is presented. This characteristic is significantly different from that of a traditional power system, and presents a new challenge for system stability. Disclosure of Invention In view of the above problems, the present invention provides an improved SEPIC converter with broadband oscillation suppression and a control method thereof. Therefore, the invention solves the key problems of low electric energy quality, limited voltage gain, low efficiency, insufficient broadband oscillation inhibition capability, insufficient adaptability to load and environmental change and the like of the existing photovoltaic power generation system in a novel power distribution network environment. In order to solve the technical problems, the invention provides a distribution network broadband oscillation suppression type improved SEPIC converter, which comprises an energy input end, an improved SEPIC converter, a broadband oscillation suppression network, a full-bridge inverter, an LC low-pass filter, a load and a control system; the energy input end is a solar photovoltaic module array and is used for providing initial direct current electric energy; the improved SEPIC converter is connected to an energy input end and used for boosting input direct-current voltage to target voltage, and comprises a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor, a third capacitor, a first diode, a second diode, a third diode, a fourth diode, a fifth switching tube and a broadband oscillation suppression network, wherein the broadband oscillation suppression network is connected to an output end of the improved SEPIC converter and used for detecting and suppressing broadband oscillation, the broadband oscillation suppression network comprises a broadband damping resistor, a broadband damping capacitor and a multi-band resonance suppression circuit, the full-bridge inverter inverts the direct-current voltage output by the improved SEPIC converter into alternating-current voltage and comprises a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, the LC low-pass filter is connected between an output end of the full-bridge inverter and a power grid and used for filtering high-frequency switching harmonic waves in output voltage of the full-bridge inverter and comprises a fourth inductor and a fourth capacitor, the load is a final energy output end is responsible for final energy output, and the full-bridge inverter is connected to an improved control system, the full-bridge inverter, the full-bridge control system, the full-bridge inverter control system and the full-bridge control system, the full-bridge control system and the improved SEPIC converter are used for generating and the full-bridge control system. The improved SEPIC converter comprises a working mode 1 and a working mode 2, wherein the working mode 1 comprises a fifth switch tube which is conducted, a first diode and a second diode are forward b