Kim Hung Le

Comparison of power quality in different grid-integrated wind turbines

Nowadays, the proportion of wind turbines and the dimensions of wind plants have increased significantly all over the world. This paper describes a comparison of the power quality for wind power systems based on three different popular wind generators: the squirrel-cage induction generator (SCIG), the doubly-fed induction generator (DFIG) and the permanent-magnet synchronous generator (PMSG). Although a fixed speed system is more simple and reliable, it severely limits the energy output of a wind turbine and power quality. In case of variable speed systems, comparisons shows that generator of similar rating can significantly enhance energy capture as well as power quality. The performances of these wind turbines and their characteristics are analyzed in steady-state. Simulation results matched well with the theoretical turbines operation.

Hybrid controller for transient stability in wind generators

In wind power plants typically squirrel-cage induction generators (SCIG) tend to drain large amount of reactive power from the grid, potentially causing a drop voltage. To improve SCIGs power quality and transient stability, this paper investigates a new pitch angle control strategy, including normal scheme and Fault-Ride-Through (FRT) scheme, based on hybrid of PI and Fuzzy logic technique. In particular, an analytic model for transient stability is implemented using the equivalent circuit of the SCIG and on the concepts of stable and unstable electrical-mechanical equilibrium. This method has been evaluated by comparing the results with the dynamic simulation. The dynamic simulation results show that the proposed hybrid controller can be effective in enhancing output power smoothness and FRT requirements for SCIG in wind power system.

Effects of bypass diode configurations on solar photovoltaic modules suffering from shading phenomenon

The temperature, radiation and other ambient environmental conditions are influencing the operation of solar cells. The shadowing phenomenon on solar cells causes the decrease of their output power. This paper analyses the effects of bypass diode configurations on photovoltaic systems operation under completely shadowed conditions. The authors analyze and propose several bypass diode configurations to limit the effects of this phenomenon and thus enhance the operational performance of photovoltaic (PV) systems. The case study deals with PSpice simulation of I–V and P-V characteristics of a real PV module type. The analysis of simulation results for I–V and P-V curves highlight the advantages and disadvantages of each type of bypass diode configuration, as well as its capability to be used in practice.

Simulation and performance analysis of a new LVRT and damping control scheme for DFIG wind turbines

Doubly-Fed Induction Generator (DFIG) Wind Turbine (WT) is rather sensitive to power system faults and requires specific power converter protection, namely a crowbar. When the crowbar is triggered, the rotor is short circuited over the crowbar impedance, the rotor-side converter (RSC) is incapacitated and therefore the DFIG operates as a squirrel-cage induction generator (SCIG) that tends to drain large amount of reactive power from the grid during fault, potentially causing a voltage drop. Therefore, in order to enhance the transient stability and damping of the electro-mechanical oscillations of a grid-connected DFIG wind farm, in this paper we propose the use of DFIG based Low-voltage Ride Through (LVRT) scheme including crowbar, RSC, GSC (Grid-side converter) and PSS (Power System Stabilizers).

A hybrid Fuzzy-PI cascade controller for transient stability improvement in DFIG wind generators

Doubly-Fed Induction Generator (DFIG) Wind Turbine (WT) can be affected by power system faults and requires crowbar protection. When the crowbar is triggered, the rotor is short circuited over the crowbar impedance, the DFIG operates as a Squirrel-cage Induction Generator (SCIG) that tends to drain large amount of reactive power from the grid during fault, potentially causing a voltage drop. In this research, therefore, we propose the use of DFIG based Low-voltage-Ride-Through (LVRT) scheme including crowbar, PSS (Power System Stabilizer), RSC (Rotor-side converter) and GSC (Grid-side converter) in order to enhance the transient stability of a grid-connected DFIG. A hybrid cascade Fuzzy-PI based controlling technique is introduced to control the Insulated gate Bipolar Transistor (IGBT) based frequency converter to enhance the transient stability. In the simulations here presented, the proposed control scheme is investigated by comparing the performance of the DFIG system with and without LVRT and damping control scheme.

Small and large signal stability analysis of IMPSA wind power plant integration on Vietnamese power system

This research presents a study on the small and large signal stability of IMPSA wind power plant with variable speed wind turbines connected to Vietnamese power system. Based on an aggregated wind park model in Power System Analysis Toolbox (PSAT) library, a dynamic model of Ninh Thuan - Binh Thuan grid, a province of Vietnam where a variable speed wind turbine system has been built. The toolboxes such as Power Flow, Time Domain Simulations in PSAT are used to study the small and large signal stability of IMPSA wind power plant and Ninh Thuan - Binh Thuan grid after the occurrence of small and large disturbances, i.e. trip lines and three phase faults, respectively. The different simulation results show how the Vietnamese Wind Power Plant (WPP), equipped with variable speed wind power generators, will respond to disturbances of the buck power system in the near future.