Snehamoy Dhar

Fault Detection and Location of Photovoltaic Based DC Microgrid Using Differential Protection Strategy

A new differential current-based fast fault detection and location scheme for multiple Photovoltaic-based dc microgrid is proposed in this paper. A multiterminal dc (MTDC) distribution network is an effective solution for present grid scenario, where local distribution is incorporated primarily by power electronics based dc loads. PV systems with auxiliary power sources and local loads are used for MTDC connection, especially when ac utility grid is integrated with it by voltage source converters. Pole to pole and pole to ground faults are basically considered as dc distribution network hazards. As PV is connected through dc cable, high resistive dc arc fault is also studied in present literature. The proposed PV system is considered with arc-fault circuit interrupters as backup protection and is used to detect arcing series fault. Fast acting dc switching is considered for proposed differential current-based unit protection. A discrete frame differential current solution is considered to classify the fault type by modified cumulative sum average approach. By calculating unknown dc cable resistance accurately by non-iterative Moore-Penrose pseudo inverse technique, the fault distance is calculated. TMS320C6713 DSP based test-bench is used for verification of the scheme.

A firefly optimized fast extreme learning machine based maximum power point tracking for stability analysis of microgrid with two stage photovoltaic generation system

This paper proposes a new Firefly optimized Ridge Extreme Learning Machine (RELM-FF) algorithm based maximum power point tracking (MPPT) investigation for stability study of photovoltaic (PV) interactive microgrid dynamics. The proposed MPPT study is effective by managing minimum uncertainty limits, during solar uncertainty conditions (i.e., inconsistent irradiation, partial shading, etc.), compared with conventional techniques. A two stage converter dynamics is considered for the proposed grid interactive PV system. To withstand stability during worst grid operating scenario (both PV side and grid side uncertainty), a robust nonlinear Lyapunov based finite time sliding mode (LFSM) control is proposed for PV-VSC (voltage source converter) system. As the proposed multiple distributed energy resources based microgrid is considered as weak (low short circuit ratio), and PV is considered as an active power source, the Q-V based state variables are used for the dynamic control loop. A small signal stability an...

Harmonic Profile Injection-Based Hybrid Active Islanding Detection Technique for PV-VSC-Based Microgrid System

In this paper, a new investigation on islanding detection method is presented for PV-based VSC system. The proposed PV-VSC is represented as one of the distributed energy resource (DER) for a microgrid environment. A new multivariable dynamic model is presented in terms of two stage conversion with a dc-dc converter for the proposed PV-VSC system. The proposed VSC system is controlled primarily by a positive sequence P-Q loop, at the PCC. A new backstepping fast sliding mode control (BFSMC) is proposed for primary PWM control of VSC system. During sudden grid disconnection an islanding protection loop based on rate of change in voltage harmonic profile injection is proposed. A binary tree (BT) threshold filter is designed for the proposed hybrid islanding protection loop, to avoid false detection during other grid operational issues. UL 1741 (section 46) standard is followed for the PV-VSC system to consider the worst-case scenario. Performance of the proposed hybrid islanding protection scheme is investigated for IEEE 9 bus system with multiple DERs, implemented in MATLAB/Simulink environment. The effectiveness of the proposed scheme is determined by result analysis, where no significant effect on power quality is recorded during nominal grid operation..

Islanding disclosure for grid interactive PV-VSC system using negative sequence voltage

This paper presents a new study on active islanding detection method for grid connected photovoltaic (PV) based voltage source converter (VSC) system. The VSC system is basically controlled by positive sequence P-Q loop, where point of common coupling (PCC) power components are measured parameters. But during grid disconnection an islanding detection loop is further implemented with existing control, based on negative sequence voltage ( neg dq V , ) at PCC. The threshold for the feedback sequence voltage is determined to maintain a negligible non detection zone (NDZ) and to avoid false detection during other power quality issues. Worst case scenario is considered by implementing a PV based VSC system from IEEE UL 1741 standard. Performance of the proposed islanding detection loop is investigated in MATLAB/ Simulink environment. The efficient detection of islanding with less than a cycle Run on time is ensured by the result analysis, where no significant effect in power quality during normal operating condition has been maintained.

Performance investigation of a Q-V-based Lyapunov finite time VSC control for grid interactive photovoltaic system

A photovoltaic (PV)-based voltage source converter (VSC) system, integrated with local load and utility grid is presented in this paper. The PV-VSC control hence considered on the reactive power (Qpv) and DC side VSC voltage (V2) errors, obtained from the measured parameters at point of common coupling (PCC) and DC side VSC capacitor respectively. The unmodelled dynamics of the phase-locked loop system (PLL) is averted for the proposed control approach as it is designed directly from instantaneous reactive power and DC voltage. A Lyapunov function-based finite time nonlinear Q-V controller is proposed to provide robustness with efficient error convergence during various micro grid operation disturbances. The performance evaluation of the proposed control during utility grid fault has been studied in MATLAB/m-file script. Validation of the proposed control is further obtained in MATLAB/Simulink environment. A conclusion is being carried out from simulation studies where the Lyapunov-based control is found efficient and robust compared with conventional PI control and feedback linearisation-based control (FLC).

A hybrid functional link extreme learning machine for Maximum Power Point Tracking of partially shaded Photovoltaic array

For maximum utilization of Photovoltaic (PV) system the Maximum Power Point tracking (MPPT) is necessary. This paper presents three novel intelligence techniques named Trigonometric Functional Link Artificial Neural Network (TFLANN), Ridge Extreme Learning Machine (RELM) and RELM with trigonometric functional expansion block (FEB) under partial shaded condition to predict the voltage at Maximum Power Point (MPP). Here the proposed techniques are compared and the results show that RELM with FEB is more efficient as compared to other two techniques in partial shaded conditions. The efficiency of the proposed methods is observed in terms of Root Mean Square Error (RMSE), Mean Absolute Percentage Error (MAPE) and Mean Absolute Error (MAE) as discussed in result analysis. The RELM with FEB is less complex and takes less time for execution as compared to RELM and TFLANN method. The proposed PV system is being implemented MATLAB/SCRIPT environment.

Harmonic profile injection based active islanding detection for PV-VSC based grid

A new harmonics profile injection based active islanding detection technique is proposed for Photovoltaic (PV) based voltage source inverter (VSI) system. Positive sequence active (Ps) and reactive power (Qs) at PCC is obtaining the multivariable control structure dynamics of the VSI, where a local perturbation of % harmonic amplification factor (%HAF) is simultaneously implemented with proper threshold. Dynamic variables, Ps and Qs is obtained from three phase voltage at PCC and VSI current to avoid unnecessary PLL angel calculation of the unmodelled VSI framework. The % HAF of PCC voltage is determined as disturbance injection parameter to the VSI P-Q control loop. Threshold before injection is determined by observation of negative sequence reactive power (Qneg) at PCC to avoid false detection. To accommodate the system with worst case handling capability, IEEE UL 1741 standard is being followed for proposed PV-VSI modeling. Performance of the proposed islanding detection technique is determined based on run on time for over/ under voltage protection (OVP/UVP). The performance study is obtained by modeling a 100 kW, 115 volt PV-VSI system integrated with utility grid in MATLAB/Simulink environment.

Finite-time sliding mode power control of grid-connected three-phase photovoltaic array

Abstract A new direct power control formulation for the voltage source converter (VSC) in a grid-connected photovoltaic (PV) array is discussed in this paper. Instead of controlling the direct- and quadrature-axis currents of the VSC through the use of a phase-locked loop system (PLL), the instantaneous real- and reactive-power components are used as control variables. This approach, therefore, does not take into account the unmodelled dynamics of the PLL resulting in a robust control of the active, reactive powers while maintaining the photovoltaic (PV) array voltage at a constant value. Further, the stability of the grid-connected PV array is enhanced by designing a Lyapunov’s function-based finite-time non-linear reactive power and dc-link voltage controller, which essentially uses the terminal sliding mode approach. To prove the robustness of the proposed approach, several system disturbances like changes in solar insolation and active and reactive power references, islanding conditions, converter parametric changes, and faults on the converter and inverter buses are considered. In all these cases, the new controller is found to enhance overall system stability in comparison to the inferior performance by the proportional-integral controller