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This paper presents a theoretical analysis and simulation for the design and implementation of a Second Order Generalized Integrator - Frequency Locked Loop (SOGI-FLL) aimed at synchronization and fault detection when connecting an inverter to the utility grid. Such an inverter is implemented in a Highly-Efficient-and-Reliable- Inverter-Concept (HERIC) topology. The two main aims of this work are:...
Multilevel line commutated inverters for renewable energy systems have gained popularity in recent times, especially in the distributed generation where a number of batteries, fuel cells, solar cell, and micro-turbines can be connected through a MLC to feed the grid. They can synthesize higher output voltage levels and can generate near sinusoidal voltages. This paper presents analysis of a grid connected...
In this paper, a high gain single-stage buck-boost grid-connected system is proposed. The proposed system consists of a high voltage gain - high efficiency - switched inductor buck-boost converter (SIBBC) and a folded cascade H-bridge inverter. The proposed converter switch is derived with a sinusoidal modulation, so that the converter output voltage is a rectified sine wave which requires only a...
The purpose of this paper is to provide low cost, high power quality and high efficiency solutions for grid-connected inverters. Compared with bipolar switched inverters, unipolar switched inverters have the advantages of higher efficiency due to reduced switching frequency and low iron losses of inductor in output filter. However, unipolar inverters produce large harmonic distortion due to the dead-time...
In this paper, a high frequency (HF)-based three-phase Semicontrolled rectifier-current source inverter system is proposed for grid-connected permanent magnet wind generators. The main advantages of the topology are: high efficiency due to less power losses and reduced number of switching elements, high output power density realization, reduced passive component ratings proportionally to the frequency,...
Distributed generation (DG), such as solar-energy-based photovoltaic (PV) systems, wind generation, and other renewable resources, is a quickly growing source of energy for today's power system. These assets pose challenges to grid reliability and power quality. One critical challenge is islanding (inadvertent system separation) detection, separation, and eventual resynchronizing. Research is underway...
The micro grid is an integrated form of distributed energy resources. The interconnection of small modular generation technologies at the medium voltage (MV) and low voltage (LV) distribution levels may affect the power system performance. This type of the networks will use the best combination of control and modeling technologies to meet the specific capacity, quality and reliability. For the MG...
Renewable energy resources (RES) are being increasingly connected in distribution systems utilizing power electronic converters. This paper presents a novel control strategy for achieving maximum benefits from these grid-interfacing inverters when installed in 3-phase 4-wire distribution systems. The inverter is controlled to perform as a multi-function device by incorporating active power filter...
In conventional grid-connected PV system, the control of real and reactive power is undertaken adjusting both modulation index and phase angle of the inverter. The maximum power point of the PV array is tracked by adjusting duty cycle of the dc-dc converter or modulation index of the inverter. The PWM pattern has to be optimized each time the index of modulation is changed which involves excessive...
This paper presents a grid-connected PV system where the PV source is replaced by a real time emulator. The PV emulator is based on a DC/DC converter controlled by the pole placement technique according to PV current-voltage characteristics. These characteristics are obtained by an analytical model whose parameters are identified on the basis of an actual PV installation. In the proposed plant the...
This paper proposes three phase grid connected anti-islanding controller based on distributed generation interconnection. This method is a combination of two detection methods namely active and passive. Firstly, Active islanding detection generates disturbances at the output of the distributed generation by use of Positive feedback and Continuous feedback signal injection which is based on DQ implementation...
This paper presents a current control for single phase grid connected inverters. The method allows for inverter active and reactive power control. The method uses the Direct-Quadrature (DQ) synchronous reference frame transformation for single-phase converters. This method transforms an orthogonal pair consisting of the inverter output current and a time shifted version of this current from a stationary...
This paper presents a grid connected system. Three phase DC-AC inverters used to convert the regulated DC power to AC power suitable for grid connection. Third harmonic injection PWM (THIPWM) was employed to reduce the total harmonic distortion and for maximum use of the voltage source. DSP was used to generate the accurate THIPWM for grid connection, by synchronizing the inverter voltage with the...
Based on the synthetic control of microgrid, a flexible power electronics interface is developed in this paper. Considering distributed generation types and storage devices, different control strategies are adopted in controller design for different distributed generation units. The interface comprises a couple of back-to-back VSC converters, and exports variable active power and reactive power in...
Grid-connected photovoltaic (PV) generation attracts increasing attention in countries around the world and it has been extensively studied during last ten years. In the literature, the control system for PV systems has been designed to respond extremely fast to changed weather condition, and the whole regulating duration is generally within tens of milliseconds. As PV installation is moving towards...
This paper discusses the dynamic voltage restorer (DVR) supported wind power generator connected to the grid to improve the low voltage ride through (LVRT) capability of the grid. The wind power generators are connected to the grid through a feeder to the distribution system and the DVR is connected to the point of common coupling (PCC), where loads are connected. The main aim of the DVR is to regulate...
This paper presents design and implementation of a 5 kW 1 φ bi-directional inverter with wide inductance variation. The bi-directional inverter can fulfill grid connection and power factor correction, in which inductor current can vary from 0 to 32A in one line cycle. This will result in wide inductance variation, around 7 times for an inductor constructed with an MPP core, and thus high current ripple...
A dual mode time-sharing inverter has higher efficiency than other type grid-connected inverter due to only one power stage of it working in high frequency state at any time. In this paper, small signal modeling of this inverter is carried out, which reveals that the control-to-grid current transfer function of this inverter has a right half plane zero at low frequency during the “Boost” operating...
Distributed power generation systems (DPGS) such as wind and solar become more and more widely spread. As a consequence grid operating companies demand system services. As part of the general fault ride through (FRT) requirements this paper deals with low voltage ride through (LVRT) capability of a three-phase-four-wire grid-tied solar inverter. The standard system will be described and necessary...
In the future, distributed generation (DG) needs to be enabled to actively participate in control of grid voltage and frequency. An efficient grid integration strategy is required to interconnect the DG to conventional power systems and to improve the power quality and reliability (PQR) as well. The main task of the interconnected system is to control and maintain frequency and voltage of the power...
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