Three-phase Grid-connected PV Inverters Research Articles

Adaptive Proportional Complex Integral Control Strategy of Three-Phase Grid-connected PV Inverter

The performance of conventional controller of three-phase grid-connected inverters possibly deteriorate during grid frequency drift. In this paper, an frequency adaptive proportional complex integral (PCI) controller with frequency locking loop (FLL) was proposed, the FLL was utilized to adjust the resonant frequency of PCI automatically, and the zero current steady error was achieved by PCI controller. The validity of the proposed control scheme was demonstrated through results of simulation and experimental.

Simulation Models For Three-Phase Grid Connected PV Inverters Enabling Current Limitation Under Unbalanced Faults

Simulation Models For Three-Phase Grid Connected PV Inverters Enabling Current Limitation Under Unbalanced Faults

Adaptive dc-link voltage control strategy to increase PV inverter lifetime

This work proposes an adaptive dc-link voltage strategy applied to a double-stage three-phase grid-connected PV inverter, in order to decrease the power devices and capacitors thermal stress, and increase the system-level reliability as a consequence. The objective is to reduce the dc-link voltage to the minimum value required to inject power into the grid. A system reliability analysis is made based on mission profiles from Brazil. The results show that the proposed technique has a positive impact on the system reliability, increasing the estimated lifetime by 75% when compared to the traditional fixed dc-link voltage strategy.

Direct power control of a grid-connected photovoltaic system using a fuzzy-logic based controller

In this paper a fuzzy logic-based controller is proposed for direct power control of three-phase grid-connected photovoltaic PV inverters. To demonstrate the effectiveness of the control method, a typical grid-connected PV inverter is implemented and the performance of the proposed technique is compared to a traditional proportional-integral PI controller. Numerical simulation results illustrate that the proposed fuzzy controller performs well in independently regulating the active and reactive output powers. Moreover, comparisons of simulation results between fuzzy and PI controllers show advantages of the fuzzy-based technique in terms of transient response characteristics, such as fast response, small overshoot, acceptable steady-state fluctuation, and high robustness.

Impact of Photovoltaic Tied to Electrical Grid System On Power Quality

The High Penetration of PV power into the existing electricity grid needs more study and analysis to enable safe operation. One of the major concerns is the impact of PV system on grid power quality .Poor power quality could cause disturbance and financial losses due to the use of power inverters. Harmonic distortion is a serious power quality problem that reduces power quality and consequently causes a number of problems to consumer and network. This Paper proposes a new strategy for power quality improvement in a three-phase grid connected PV Inverter with central and string configuration and controlling on them using Sinusoidal pulse width modulation and space vector modulation methods with LCL Filter .This paper investigates PV Inverter configuration and impact of them on PV Plant Performance and harmonics that produced by PV inverter. The design, modeling, and analysis of a grid-tied PV system were performed in the PSCAD software simulation environment. The simulations of Harmonic Distortion (Total Demand Distortion & Total Harmonic Distortion) were applied at Point of Coming Coupling and the results obtained were compared with the limits specified by IEEE STD 519-1992 standards.

Performance evaluation of WPT based islanding detection for grid-connected PV systems

Abstract Recent developments in power electronics technology have emerged towards the generation of electrical power from the renewable energy sources. Among renewable energy sources, solar energy has garnered more importance because of less maintenance and environmental friendly. In grid connected mode, distributed power generation system (DPGS) requires reliable islanding detection technique to find the electrical grid status and operate the grid connected inverter effectively. This paper investigates a comparative performance analysis of wavelet transform (WT) and wavelet packet transform (WPT) based detection in a three-phase grid connected PV inverter system under various power quality disturbances and islanding situation. The WT and WPT coefficients are determined by applying db4 wavelet basis functions, which are obtained optimally for analyzing perturbations that occur in grid connected PV system. The wavelet transform produces large errors due to spectral leakages in frequency bands. On the other hand, WPT provides uniform frequency subband with better time frequency resolution over WT. Finally, the feasibility of proposed WPT based islanding detection method is verified by simulating the system in MATLAB/SIMULINK environment. The simulated results demonstrate the better performance of WPT over WT technique and proved as an accurate, fast and reliable detection technique.

Fault Diagnosis and Fault-Tolerant Control of DC-link Voltage Sensor for Two-stage Three-Phase Grid-Connected PV Inverters

This paper proposes a method for fault diagnosis and fault-tolerant control of DC-link voltage sensor for two-stage three-phase grid-connected PV inverters. Generally, the front-end DC-DC boost converter tracks the maximum power point (MPP) of PV array and the rear-end DC-AC inverter is used to generate a sinusoidal output current and keep the DC-link voltage constant. In this system, a sensor is essential for power conversion. A sensor fault is detected when there is an error between the sensed and estimated values, which are obtained from a DC-link voltage sensorless algorithm. Fault- tolerant control is achieved by using the estimated values. A deadbeat current controller is used to meet the dynamic characteristic of the proposed algorithm. The proposed algorithm is validated by simulation and experiment results.