scholarly journals A rapid harmonic detection method for grid-connected photovoltaic when three-phase voltage is unbalanced

2021 ◽  
Author(s):  
Tiezhou Wu ◽  
An Wang ◽  
Yawen Xu
Keyword(s):  
Phase Angle ◽  
Detection Method ◽  
Positive Sequence ◽  
Harmonic Detection ◽  
Phase Voltage ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Negative Sequence ◽  
Three Phase ◽  
Low Pass

Abstract By using power electronic devices, photovoltaic grid-connected power generation may inject harmonics into the power system. As the photovoltaic grid-connected inverter has the same basic structure as the active power filter, so the unified control of the photovoltaic grid and active filtering can be achieved. When the current unified control system compensates harmonics of the grid side, it mainly uses ip-iq harmonic detection method, which is based on instantaneous reactive power theory. When the three-phase voltage is unbalanced, the method has a large voltage phase angle detection error and the signal of the low-pass filter tracking system is long, detection time delay and even failure occur. This paper proposes an improved fast harmonic detection method. When phase deviation or amplitude change occurs to the three-phase voltage, the positive and negative-sequence voltages are simultaneously park transformed. The negative-sequence component is filtered by the current average module to obtain the fundamental amount of the voltage, then the phase angle of the positive-sequence voltage is accurately calculated to improve the harmonic current detection accuracy. Through the study of the integral method, it is found that the least common multiple of each harmonic period can be used as the integral interval, and the integral value is also zero, so the detection delay time is reduced by replacing the low-pass filter with an integration module. The simulation results show that the proposed harmonic detection algorithm can accurately detect harmonics when the three-phase voltage is unbalanced, and about 0.057 s improve the harmonic detection speed compared with the commonly used ip-iq method.

scholarly journals Study of Harmonic Detection Methods under Non-Ideal Conditions in Ship Power Network

2015 ◽  
Vol 22 (3) ◽  
pp. 82-89
Author(s):  
Xiao-Yan Xu ◽  
Janusz Mindykowski ◽  
Tomasz Tarasiuk ◽  
Chen Cheng
Keyword(s):  
Phase Lock Loop ◽  
Mean Value ◽  
Detection Methods ◽  
Harmonic Detection ◽  
Phase Voltage ◽  
Rapid Variation ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Three Phase ◽  
In Series

Abstract An improved harmonic detection method based on average arithmetic is proposed. According to the research results, the designed solution uses an LPF (low-pass-filter) and a mean value module connected in series instead of the conventional mean value module, and simultaneously, a three-phase voltage phase-locked module instead of commonly used PLL (phase lock loop) module is applied in order to reduce the influence caused by three-phase distorted voltage and rapid variation of load. The experimental results show that the application of this solution leads to increase in the accuracy of harmonics detection for distorted three-phase voltage and rapid variation of load.

scholarly journals Improvement of DSOGI PLL Synchronization Algorithm with Filter on Three-Phase Grid-connected Photovoltaic System

2018 ◽  
Vol 18 (1) ◽  
pp. 35 ◽  
Author(s):  
Rofiatul Izah ◽  
Subiyanto Subiyanto ◽  
Dhidik Prastiyanto
Keyword(s):  
Reference Frame ◽  
Frequency Estimation ◽  
Photovoltaic System ◽  
Positive Sequence ◽  
Pv System ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Synchronous Reference Frame ◽  
Three Phase ◽  
Low Pass

Synchronous Reference Frame Phase Locked Loop (SRF PLL) has been widely used for synchronization three-phase grid-connected photovoltaic (PV) system. On the grid fault, SRF PLL distorted by negative sequence component and grid harmonic that caused an error in estimating parameter because of ripple and oscillation. This work combined SRF PLL with Dual Second Order Generalized Integrator (DSOGI) and filter to minimize ripple and minimize oscillation in the phase estimation and frequency estimation. DSOGI was used for filtering and obtaining the 90o shifted versions from the vαβ signals. These signals (vαβ) were generated from three phase grid voltage signal using Clarke transform. The vαβ signal was the inputs to the positive-sequence calculator (PSC). The positive-sequence vαβ was transformed to the dq synchronous reference frame and became an input to SRF-PLL to create the estimation frequency. This estimation frequency from SRF PLL was filtered by the low-pass filter to decrease grid harmonic. Moreover, the output of low-pass filter was a frequency adaptive. The performance of DSOGI PLL with filter is compared with DSOGI PLL, SRF PLL, and IEEE standard 1547(TM)-2003. The improvement of DSOGI PLL with filter gave better performances than DSOGI PLL and SRF PLLbecause it minimized ripples and oscillations in the phase and frequency estimations.

scholarly journals Improved harmonic detection method based on ip-iq theory

2021 ◽  
Vol 261 ◽  
pp. 01028
Author(s):  
Zhisen Yao ◽  
Guige Gao
Keyword(s):  
Detection Method ◽  
Phase Error ◽  
Response Speed ◽  
Detection Accuracy ◽  
Harmonic Detection ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
In Series ◽  
Filtering Effect

Based on the traditional ip-iq harmonic detection theory, the accuracy of harmonic detection is easily affected by the phase-locked loop (PLL) output phase error, and the single low-pass filter (LPF) detection accuracy and filtering effect cannot be simultaneously. In this paper, an improved harmonic detection method based on the second-order generalized integrator-frequency locked loop (SOGI-FLL) technique is proposed to generate sine and cosine signals with the same frequency as the grid voltage; The traditional low-pass filter and average filter are used in series to improve the response speed and accuracy. Through theoretical analysis of the improved harmonic detection method and simulation in MATLAB environment, the theory and simulation results prove the effectiveness of the improved method.

scholarly journals Control Strategy for Grid Connected Inverters Under Unbalanced Network Conditions - A DOb Based Decoupled Current Approach

2017 ◽  
Author(s):  
Emre Ozsoy ◽  
Sanjeevikumar Padmanaban ◽  
Lucian Mihet-Popa ◽  
Viliam Fedák ◽  
Fiaz Ahmad ◽  
...  
Keyword(s):  
Control Strategy ◽  
Current Approach ◽  
Current Control ◽  
Positive Sequence ◽  
Voltage Source ◽  
Renewable Sources ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Negative Sequence ◽  
Low Pass

Penetration of grid connected inverters (GCI) has arisen in power systems due to increasing integration of renewable sources. However, restrictive grid codes require that renewable sources connected to the grid with power electronic systems must be properly connected and appropriate currents must be injected to support stability of the grid under grid faults. Simultaneous injection of symmetrical positive and negative sequence currents is mandatory to support stabilization of grid at the instant of grid faults. Conventional synchronously rotating frame dq current controllers are insufficient under grid faults due to low bandwidth of PI controllers. This paper proposes a new grid current control strategy for grid connected voltage source inverters under unbalanced grid voltage conditions. A proportional current controller with a first order low pass filter disturbance observer (DOb) is proposed which establishes positive sequence power requirements and independently control negative sequence current components under unbalanced voltage conditions. The method does not need any parameter, since it estimates nonlinear terms with low pass filter DOb. Simulations are implemented in Matlab/Simulink platform demonstrating the effectiveness of proposed method.

Adaptive Low-Pass Filter Based DC Offset Removal Technique for Three-Phase PLLs

2018 ◽  
Vol 65 (11) ◽  
pp. 9025-9029 ◽  
Author(s):  
Parag Kanjiya ◽  
Vinod Khadkikar ◽  
Mohamed Shawky El Moursi
Keyword(s):  
Pass Filter ◽  
Low Pass Filter ◽  
Dc Offset ◽  
Three Phase ◽  
Low Pass ◽  
Removal Technique

Disturbance-observer based control of voltage-source-converter under unbalanced voltage conditions

2017 ◽  
Vol 14 (6) ◽  
pp. 522-531 ◽  
Author(s):  
Akhtar Rasool ◽  
Esref Emre Ozsoy ◽  
Fiaz Ahmad ◽  
Asif Sabanoviç ◽  
Sanjeevikumar Padmanaban
Keyword(s):  
Disturbance Observer ◽  
Operating Conditions ◽  
Voltage Source ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Content Type ◽  
Negative Sequence ◽  
First Order ◽  
Unbalanced Voltage ◽  
Low Pass

Purpose This paper aims to propose a novel grid current control strategy for grid-connected voltage source converters (VSCs) under unbalanced grid voltage conditions. Design/methodology/approach A grid voltage dynamic model is represented in symmetrical positive and negative sequence reference frames. A proportional controller structure with a first-order low-pass filter disturbance observer (DOB) is designed for power control in unbalanced voltage conditions. This controller is capable of meeting the positive sequence power requirements, and it also eliminates negative sequence power components which cause double-frequency oscillations on power. The symmetrical components are calculated by using the second-order generalized integrator-based observer, which accurately estimates the symmetrical components. Findings Proportional current controllers are sufficient in this study in a wide range of operating conditions, as DOB accurately estimates and feed-forwards nonlinear terms which may be deteriorated by physical and operating conditions. This is the first reported scheme which estimates the VSC disturbances in terms of symmetrical component decomposition and the DOB concept. Originality/value The proposed method does not require any grid parameter to be known, as it estimates nonlinear terms with a first-order low-pass filter DOB. The proposed control system is implemented on a dSPACE ds1103 digital controller by using a three-phase, three-wire VSC.

Operation of an induction motor supplied by voltage containing subharmonics

2017 ◽  
Vol 1 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Tomasz Drabek
Keyword(s):  
Induction Motor ◽  
Power Supply ◽  
Induction Machine ◽  
Induction Machines ◽  
Positive Sequence ◽  
Rotor Speed ◽  
Phase Voltage ◽  
Negative Sequence ◽  
Three Phase

The paper discusses the effects of the presence of subharmonics (i.e. frequencies lower than the basic 50 Hz) in the voltage supplying the induction machine. Subharmonics in a three-phase grid are the result of the oscillations of peak values of the voltages. In induction machines, this results in the subharmonic and interharmonic currents, the generation of alternating moments, the increase in the rms value of the current of the fundamental harmonic and the oscillations of the rotor speed. In the paper is derived expression on the thermally acceptable load of the motor (by torque and power), in the case of supplying it by three-phase voltage containing a positive sequence of subharmonics. It presented the obstacles to derive the analogical expression for power supply containing a negative sequence of subharmonics.

The Analysis and Design of Three-Phase Static Inverter Deadband Effect and Harmonic Suppression

2013 ◽  
Vol 575-576 ◽  
pp. 293-296
Author(s):  
Qun Min Yan
Keyword(s):  
Control Method ◽  
Design Method ◽  
Harmonic Suppression ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Analysis And Design ◽  
Three Phase ◽  
Low Pass ◽  
Harmonic Components ◽  
Simulated Analysis

in order to solve the problem of three-phase static inverter output waveform distortion, detailed analyzed of the voltage distortion caused by the deadband effect and the resulting harmonic components. The control method is proposed to set the deadband time combining with the voltage compensation, while in order to improve the inverter output, the converter output to design a trap filter and a low pass filter cascaded filtering circuit. Simulated analysis the entire system though Saber, using the digital chip TMS320F2812 to achieve appropriate compensation strategies, simulation results and experimental results have all proved the effectiveness of the design method.

scholarly journals An improved ip-iq harmonic detection method

2021 ◽  
Vol 248 ◽  
pp. 02045
Author(s):  
Yang Guoqing ◽  
Yan Kai ◽  
Wang Deyi ◽  
Chai Yuan ◽  
He Xu
Keyword(s):  
Reactive Power ◽  
Detection Method ◽  
Moving Average ◽  
Notch Filter ◽  
Positive Sequence ◽  
Harmonic Detection ◽  
Grid Voltage ◽  
Adaptive Notch Filter ◽  
Voltage Signal ◽  
Low Pass

The ip-iq harmonic detection method based on instantaneous reactive power has been widely used in active power filter (APF). However, the traditional ip-iq detection method has errors when the grid voltage is unbalanced and distorted. This paper proposes an improved ip-iq harmonic detection method, which uses adaptive notch filter (ANF) to extract the fundamental positive-sequence voltage signal, so that the phase locked loop (PLL) can still accurately obtain the phase information under bad grid conditions. At the same time, moving average filter (MAF) is used to replace low-pass filtering to reduce the detection delay. The simulation results show that the improved ip-iq detection method can accurately detect harmonic current under non-ideal grid voltage conditions, and has good dynamic characteristics.

DC-Bus Voltage Control Strategy Based on Low-Pass Filter for Three-Phase Four-Wire APF

2013 ◽  
Vol 732-733 ◽  
pp. 1167-1170
Author(s):  
Xia Feng ◽  
Xiao Jian Zhong ◽  
Qun Wei Xu ◽  
Guo Zhu Chen
Keyword(s):  
Voltage Control ◽  
Stable Operation ◽  
Voltage Control Strategy ◽  
Signal Model ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Three Phase ◽  
Low Pass ◽  
Dc Bus ◽  
Bus Voltage

The DC-bus voltage control is critical for stable operation of the three-phase four-wire Active Power Filter. DC-bus stable voltage loop and balance voltage loop are established based on the small signal model. Considering the disadvantages of the traditional PI control, second-order low-pass filter is introduced into the proposed controller. Simulation and experimental results are conducted to validate the effectiveness of the proposed strategy.

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