Grid Parameter Variation Research Articles

A Fault Detection Algorithm Based on Artificial Neural Network Threshold Selection in Multi-Terminal DC Grids

The DC fault is one of the critical challenges in the High Voltage Multi-Terminal Direct Current (HV-MTDC) grid. The fixed value threshold used in some implementations may be affected by different grid conditions and thus causes errors in the fault detection procedure. This paper offers a two-stage fault detection algorithm based on the integrated Artificial Neural Network (ANN) and Discrete Wavelet Transform (DWT) theory. The main innovations of the proposed method are: 1) Increasing the reliability of the fault detection operation by solving the fixed value threshold problems; 2) Offering high robustness against the wide range of fault resistances; 3) Providing bus protection capability and 4) Setting relays locally, and avoiding the requirement to high-speed communications links. Also, it offers DC fault detection in a short period of time. The performance of the proposed protection scheme has been ascertained via simulations in the MATLAB/Simulink environment. The results prove the robustness of the proposed method against noise disturbance, high resistance fault, and grid parameters variations.

Robust Frequency Cascaded Adaptive Complex Filter Control for Grid Interactive PV System

This article deals with a robust frequency cascaded adaptive complex filter (ACF) control for the grid interactive photovoltaic (PV) system. The incorporated control algorithm rejects lower order harmonics too unlike the conventional quadrature signal generators; thus, this control algorithm extracts accurate fundamental frequency orthogonal components of load current. The voltage source converter (VSC) acts as a distribution static compensator (DSTATCOM) when generation from the PV array is unavailable, besides injecting active power in the distribution network, and reducing reactive power loading on the utility network by mitigating harmonics in presence of generation from the PV array. Thus, the VSC utility is enhanced. This PV system performance is robust against the weak utility grid parameter variation and at load perturbation. The presented algorithm improves transient response at dynamic loading and irradiance change. The harmonic contents in distribution network voltage and utility current are reduced within the IEEE-519 standard.

Control of asymmetrical cascaded multilevel inverter for a grid‐connected photovoltaic system

This article presents a generalised asymmetrical cascaded multilevel inverter (MLI) for a single-phase grid-connected photovoltaic (PV) system and their control strategy. The control strategy, including maximum power tracking along with a suitable interface, is implemented for maximum power transfer from the PV source to the single-phase low-power grid. The balancing of DC-link voltages for an asymmetrical MLI under variable solar parameters as well as grid parameter variation is implemented using the proposed control strategy. The voltage controllers maintain the constant DC-link voltage ratio, whereas the current controller injects the sinusoidal current into the grid at unity power factor and track the grid voltage under variation of grid voltage using grid tracker. Stability analysis of the proposed grid-connected asymmetrical inverter system is also incorporated. The whole grid-tied PV system is simulated in the MATLAB/SIMULINK environment and the exhaustive simulation results of the system under different transient conditions are presented. In addition, a laboratory prototype for a low-power grid-tied PV system has been developed and implemented using DS1103. The performance of the system is also tested at varying irradiance conditions and the corresponding experimental results are also presented.

Requirement analysis of hybrid direct current breaker in multi‐terminal high‐voltage direct current grids

Hybrid direct current circuit breakers (DCCB) are the most adopted solution to clear high DC fault currents in short time. Existing literature does not analyse recently validated commercial breakers. This article provides an overview about hybrid DCCB and a list of criteria to evaluate and compare the performance of existing or new DCCB designs. Additionally, general measures are proposed to assess the suitability of the DCCB in a specific grid situation. Accordingly, the fault current evolution under pole-to-pole faults in different parts of a multi-terminal DC grid is analysed by means of mesh analysis with matrix differential equations. Finally, a grid parameter variation analysis is carried out through PSCAD-EMT simulations to compare the presented DCCB concepts.

A RSSI-based parameter tracking strategy for constrained position localization

In this paper, a received signal strength indicator (RSSI)-based parameter tracking strategy for constrained position localization is proposed. To estimate channel model parameters, least mean squares method (LMS) is associated with the trilateration method. In the context of applications where the positions are constrained on a grid, a novel tracking strategy is proposed to determine the real position and obtain the actual parameters in the monitored region. Based on practical data acquired from a real localization system, an experimental channel model is constructed to provide RSSI values and verify the proposed tracking strategy. Quantitative criteria are given to guarantee the efficiency of the proposed tracking strategy by providing a trade-off between the grid resolution and parameter variation. The simulation results show a good behavior of the proposed tracking strategy in the presence of space-time variation of the propagation channel. Compared with the existing RSSI-based algorithms, the proposed tracking strategy exhibits better localization accuracy but consumes more calculation time. In addition, a tracking test is performed to validate the effectiveness of the proposed tracking strategy.

Robust Line-Voltage Sensorless Control and Synchronization of LCL -Filtered Distributed Generation Inverters for High Power Quality Grid Connection

This paper presents a robust control scheme for high power quality grid connection of inductor–capacitor–inductor (LCL)-filtered distributed generation (DG) inverters. The presence of the LCL filter complicates the dynamics of the inverter control system, particularly when the uncertain nature of the grid background distortion and system parameters is considered. The proposed scheme addresses such practical difficulties by providing: 1) robust and simple active damping control performance under grid and filter parameter variation; 2) suppression of grid-induced distortion without a-priori knowledge of the grid background distortion and unbalance via real-time generation of the frequency modes and disturbances that should be eliminated from the closed-loop current control system; 3) robust deadbeat digital control performance that maximizes the dynamic performance of the converter; and 4) robustness against interaction dynamics between active damping and current tracking controllers. Furthermore, the proposed control scheme facilitates line-voltage sensorless current control and grid-synchronization performance, which enhances the reliability and cost measures of the DG interface. Theoretical analysis and comparative evaluation results are presented to demonstrate the effectiveness of the proposed control scheme.

Voltage Dip Mitigation Using Shunt-Connected Voltage Source Converter

In this paper, a voltage source converter (VSC) connected in shunt with the grid to mitigate voltage dips for sensitive processes is presented. The VSC maintains the magnitude of the grid voltage at the connection point constant by injecting reactive power to compensate for the voltage dip. This is achieved by using a cascade controller, constituted by an inner vector current-controller (VCC) and an outer voltage controller, which calculates the current references for the VCC. The paper shows that using an inductor/capacitor/inductor (LCL)-filter instead of the simpler L-filter in between the VSC and the grid yields high performance and robust controller. Furthermore, in order to compensate for unbalanced dips, both positive- and negative-sequence components of the grid voltage must be controlled separately. This is done by using two independent controllers for the two sequences, with the same cascaded structure described above. Simulation results under balanced and unbalanced dips are presented to show the performance. Also, stability analyses are done to determine the robustness of the system against grid parameter variation.