Naji Al Sayari

A Multitasking Control Algorithm for Grid-Connected Inverters in Distributed Generation Applications Using Adaptive Noise Cancellation Filters

This paper proposes a multitasking control algorithm for grid-connected inverters (GCIs) in distributed generation (DG) applications. A single-phase H-bridge voltage source inverter is used as a power electronic interface between the DG system and the grid. The proposed control algorithm operates the GCI in current control mode to achieve desired active power injection to the grid. In addition to active power injection, the proposed control algorithm has current harmonics mitigation and reactive power compensation capabilities for power quality enhancement. The control algorithm utilizes only the remaining capacity of the GCI for power quality improvement. The proposed control algorithm employs a current decomposition structure based on multiple adaptive noise cancellation (ANC) filters for extraction of harmonic and reactive currents of the local loads. The extracted harmonics are used in estimating compensating currents to be injected by the GCI. A single-phase phase-locked loop (PLL) using ANC filters has been developed to synchronize the GCI at fundamental frequency, which makes the proposed control algorithm adaptive to grid frequency fluctuations and immune to grid voltage distortions. The effectiveness of the proposed control is illustrated through computer simulation and experimental results. The influence of PLL dynamics on GCI performance has also been studied using results.

Adaptive notch filter based multipurpose control scheme for grid-interfaced three-phase four-wire DG inverter

The power electronic converter and its control system form an integral part of distributed generation (DG) systems interfacing renewable energy sources to the utility network. This paper proposes an adaptive notch filter-based multipurpose control scheme for grid interfacing DG inverter under corrupted grid conditions. The proposed control scheme uses a frequency adaptive sequence components extractor which is capable of extracting instantaneous symmetrical components and harmonic components of three-phase signals. The DG inverter in this study consists of three single-phase voltage source inverters with common dc bus and coupled to utility grid via three single-phase transformers. The DG sources are represented as constant dc voltage source on its dc side. The proposed control scheme enables the DG inverter to perform multiple tasks such as: reference power injection to grid, load reactive power support and compensation of harmonic, unbalanced and neutral currents. The effectiveness of the proposed control scheme is evaluated through MATLAB/Simulink simulations and experimentally verified using a hardware-in-the-loop (HIL)-based system.

Mitigation of harmonics in drilling rigs using shunt active power filters

Harmonics and low power factor are major concerns in modern industry. Even though several solutions are available, mitigating these problems in already established heavy industries is still a challenge. On-shore oil rigs are one such case where the problem becomes unique because of the extreme operating conditions and limited space. This paper presents a case study of mitigating the harmonic problem in on-shore oil rigs operating in deserts. It is proposed to use multiple shunt active power filters. One or more shunt active filters may go out of operation but the drives continue to run without filters resulting in distortion of voltage. The active filters which are in operations should work under distorted voltage conditions. Operation of shunt active power filter under distorted voltages is demonstrated both through simulation and experiments.

Flexible control for small power generation employing renewable energy source used in isolated communities

The controllability of the electrical production is the main problem of renewable energy generators due to uncontrollable meteorological conditions. This study examines the feasibility for an isolated small power generation based on renewable energy source able to supplying different type of loads AC and DC with regulated voltage. The complete system is modelled in Matlab\Simulink with three closed loops under fluctuation of the source (variable prime mover of the generators) and sudden application of loads. Both the DC voltage and AC voltage are controlled to the desired reference. The present results show the effectiveness and validity of the proposed power generation system.

Seamless transition scheme between grid-tied and stand-alone modes of distributed generation inverters

In this paper, an enhanced control strategy of the smooth transition between the grid-tied and stand-alone operation modes of the distributed generation (DG) inverter is proposed. In the grid-connected mode, the DG inverter controls active and reactive powers flowing into the grid by regulating grid currents using typical proportional integral plus resonant (PI+R) controllers, while direct voltage controllers utilizing a feedback linearization (FBLN) technique are applied to control the load voltages in the stand-alone mode. Applying the FBLN control gives a better performance than those of using the linear control methods for the DG inverter, which possesses a nonlinear relation between the inverter terminal and load voltages. Furthermore, initiating the value of integral terms in the PI+R regulators and FBLN as null at the instances of the operation mode changes results in a smooth transition between the current and voltage controllers for the grid-tied and stand-alone modes, respectively. The PSIM simulation results are shown to verify the feasibility of the proposed control strategy.

Adaptive Notch Filter-Based Multipurpose Control Scheme for Grid-Interfaced Three-Phase Four-Wire DG Inverter

The power electronic converter and its control system form an integral part of distributed generation (DG) systems interfacing renewable energy sources to the utility network. This paper proposes an adaptive notch filter-based multipurpose control scheme for grid interfacing DG inverter under corrupted grid conditions. The proposed control scheme uses a frequency adaptive sequence components extractor, which is capable of extracting instantaneous symmetrical components and harmonic components of three-phase signals. The DG inverter in this study consists of three single-phase voltage source inverters with common dc bus and coupled to utility grid via three single-phase transformers. The proposed control scheme enables the DG inverter to perform multiple tasks such as reference power injection to grid, low voltage ride through, load reactive power support, and compensation of harmonic, unbalanced, and neutral currents. The efficacy of the proposed control scheme is evaluated through MATLAB/Simulink simulations and experimentally verified using a hardware-in-the-loop based system.

Real-time simulation based performance analysis of active filters for oil drilling rigs

In this paper performance analysis of active power filter (APF) is studied for oil drilling rigs through real-time simulation. A typical oil drilling rig consisting of adjustable speed drives powered by diesel engine generators is modelled and simulated. Conventional filters are not suitable for autonomous power systems as the system is not stiff bus system. APF are better suited for this application. Performance of filters can be tuned and assessed accurately if they are tested under actual operating conditions of the rig, particularly weak bus and dynamic loading characteristics. A real-time test procedure to experimentally test the performance of APF connected to a diesel generator and drive system is developed. Then the drives are loaded as per the data collected from rig over a drilling cycle and harmonic filtering performance of APF is studied. In this method, dynamic models of diesel engine, synchronous generator, AC/DC converter and DC drive are solved on a digital signal processor in real time and the solution is fed to current controller controlling a voltage source inverter to emulate the oil rig system. A physical shunt APF is then connected to the setup and its dynamic performance is evaluated while load is changing. Dynamic models of for all the components are presented and simplifications are suggested so as to reduce the computational need of processor. These models are validated through computer simulations by comparing with detailed models.