Mohammad S. Widyan

Operational performance stability of grid-connected photovoltaic generator via DC–DC converter and 48-pulse voltage source inverter

Abstract This paper presents detailed steady-state stability analysis of PV generator interfaced to grid via DC–DC buck–boost converter, 48-pulse DC–AC sinusoidal Voltage Source Inverter (VSI), LC filter and transmission line. The main purpose of the DC–DC converter implementation is to inject the voltage corresponding to the Maximum Power Point of the PV generator. 48-pulse VSI is chosen as the harmonic contents in the output voltage are far away from the fundamental frequency with very small magnitudes. For numerical simulations, the complete nonlinear dynamical mathematical model in dq stationary reference frame is used including that of the terminal characteristics of the PV generator. The study comprises eigenvalues of the linearized model at various solar intensities. The robustness of the system operating point is checked by time domain simulations after small perturbations in the gird voltage and step changes on the solar insolations. Historically, series compensation of transmission lines has been used to increase the power transfer capability of the power system. In this study, the impact of equipping the transmission line with series capacitor on the system performance is highlighted. Furthermore, the effect of partial shading of the PV modules on the stability of the proposed power plant is investigated.

Dynamic and Steady-State Characteristics of Dc Machines Fed by Photovoltaic Systems

Abstract This paper presents the dynamical model and analysis of DC shunt, series and permanent-magnet (PM) motors fed by photovoltaic (PV) energy systems at different illuminations. At the full solar intensity, the maximum power point of current/voltage (I/V) characteristic of the PV modules is designed to be at the rated conditions of the machines. The nonlinear behaviour of I/V characteristics of the PV modules and that of the magnetization curve of the ferromagnetic materials of the machines are approximated by polynomial curve fitting. The dynamical analysis of the machines fed by fixed terminal voltage has also been carried out and a comparison between the cases of supplying the motors by fully illuminated solar cells, partially illuminated solar cells and fixed terminal voltage is addressed. The steady-state output characteristics, and the torque-speed characteristics, of the three DC motors with the two inputs are presented and compared. All the simulations are executed using MATLAB.

Investigation of the shunting effects of parallel-connected a-Si:H solar cells

This paper investigates the performance of parallel-connected amorphous silicon (a-Si:H) solar cells based on the separation of the shunting effects of individual cells under different illumination intensities, Φ. The cells are arranged in photovoltaic (PV) modules to meet the desired electrical requirements. According to traditional methods of determining the shunt resistance of each cell, one has to remove the lamination over the PV modules, resulting in a probable damage of the physical connections between the cells. Therefore, to solve such a problem, we make use of the illumination-intensity dependence of the shunt resistance of a-Si:H solar cells. The purpose of this study is to determine the shunt resistance of any cell in the PV module even without accessing the electrical contacts of the corresponding cell, and consequently, we non-destructively identify any shunted (low quality) cell in the PV module.

CONTROLLING SSR OF THE IEEE SECOND BENCHMARK MODEL USING TCSC AND SSSC: A COMPARATIVE STUDY

Abstract This paper investigates the effect of using two types of flexible alternating current transmission system (FACTS) devices on sub-synchronous resonance (SSR) phenomenon in power system. The devises are thyristor controlled series capacitor (TCSC) and static synchronous series compensator (SSSC .)The system under study, which is the first system of the IEEE second benchmark model of SSR, is modified such that the conventional variable series capacitor is replaced by TCSC and SSSC. The effects of TCSC and SSSC controllers are studied in terms of stability and damping. The stability of the operating point of TCSC- and SSSC-compensated systems is analysed using eigenvalue analysis of the linearized model. Time domain simulations based on the nonlinear model have also been carried out. It is found that both TCSC and SSSC have increased the operating point stability regions.

Perturbation and observation as MPPT algorithm applied on the transient analysis of PV-powered DC series motor

This paper presents the Perturbation and Observation (P&O) algorithm as Maximum Power Point Tracking (MPPT) method for the transient and steady-state analysis of DC series motor fed from Photovoltaic (PV) generator at different solar irradiance levels and various motor loading conditions. At each solar intensity, the maximum power point of Voltage/Current (V/I) characteristic of the PV generator is achieved by perturbation and observation algorithm. The dynamical analysis of the system is carried out at different solar intensities. The dynamical analysis has been further investigated after step changes in solar intensity levels with fixed load coupled to the motor. The steady-state behavior of the DC series motor is addressed at various solar irradiance levels. All numerical simulations are executed using MATLAB software package by building the code.

Modelling, simulations and operational performance of synchronous motor powered and excited by photovoltaic generators with fixed injected voltages

This paper aims to provide the operational performance of three-phase synchronous motor (SM) powered and excited by photovoltaic (PV) generators with fixed injected voltages. The two PV generators are interfaced via buck-boost choppers. Three-phase sinusoidal inverter terminated by LC filter is integrated between the chopper circuit and the stator windings of the motor. The main idea behind incorporating the chopper circuit is to power the armature and field circuits of the motor via fixed voltages at all practical solar irradiance levels and motor loading conditions. The analysis includes the system response following successive step changes of the mechanical load coupled to the motor, successive step changes of the solar irradiance levels and successive step changes of the set value of the excitation voltage. It is concluded that feeding and exciting the synchronous motor via PV generators simultaneously with fixed voltages can be practically realised at a wide range of solar irradiance levels and loading conditions even when the PV generator is partially shaded.