J. G. Trapp

Psim mathematical tools to simulate pem fuel cells including the power converter

This paper presents a mathematical model for proton exchange membrane fuel cells (PEMFCs) taking into account the basic electrochemical equations but including the boost power converter. This approaching is suitable for design and simulation of power electronics systems with embedded FCs as power supplies. The simplified model uses the Kirchoffs Voltage Law (KVL) applied to the conventional electric equivalent model of PEMFCs. This work is fully implemented in PSimTM as a general mathematical model and referred to literature data including the Boost converter, mostly used as the power interface for FCs. In this way, the model is fully evaluated by viewing the interface just as a power converter.

Variable speed wind turbine using the squirrel cage induction generator with reduced converter power rating for stand-alone energy systems

This paper presents a new configuration for a wind energy conversion system (WECS) with variable speed, using a squirrel cage induction generator (SCIG) for stand-alone energy system applications. The Proposed configuration utilizes converters with reduced power rating, operates with MPPT to maximum wind energy extraction, uses battery bank for energy storage and can operate with non-linear and unbalanced loads. Energy storage characteristic is desirable for wind energy conversion systems isolated from the mains since an energy interruption does not stop of the entire system. Also, the power rating of the converters is reduced compared to the generator and load power rating due to the low power requirements of the power converters to SCIG excitation control and to supply the load. It is presented also the whole proposed WECS and the system operation modes according the turbine speed. It is presented also the whole proposed system and the system operation modes according the turbine speed. The simulation of the proposed WECS is performed in conjunction with the dynamic wind turbine model of 1 kW and the results confirm the effectiveness to supply unbalanced and non-linear loads, the converters power rating reduction and operation with variable turbine speed. Simulation results show the effectiveness of the system to supply unbalanced and non-linear stand alone loads.

New methodology to determinate photovoltaic parameters of solar panels

This paper presents a discussion about a methodology to obtain the main parameters of solar panels and power converters in photovoltaic systems. This study is essential to obtain the maximum power transfer from the PV source to the mains grid or a load. It is also presented a formal mathematical model based on the experimental data acquisition of the key parameters of a photovoltaic cell which are: shunt and series resistances, photo generated current, the ideality factor and the diode reverse saturation current.

Stand alone self-excited induction generator with reduced excitation capacitors at fixed speed

This paper proposes a reduction of the self-excitation capacitance of induction generators by using an associated Two-Stage Matrix Converter (TSMC). This association regulates load frequency and load voltage in addition to an improved generated voltage. The resistive load affects the self-excited induction generator (SEIG) voltage, but inductive loads cause poor regulating voltage. This trend is due to the opposition between the inductive load reactance and the reactance of the self-excitation capacitors. The TSMC supplies a sinusoidal current with reduced harmonic content. Thus, the matrix converter operates as a resistive load across the IG terminals, improving regulation of the generated voltage. In this text it is included some simulation results of a 1 kW SEIG dynamic model connected either directly to the load or through the TSMC. The simulations are compared with the TSMC prototype for a similar induction machine to prove the effectiveness of the proposed control.

DC electronic load based on an interleaved chopper converter to determine photovoltaic panel and fuel cell biasing curves

This paper presents the description of a DC electronic load based on an interleaved chopper converter to determine the biasing and dynamics characteristics of either fuel cells (FCs) and photovoltaic panels (PVs). Variable loads are used for experimental data acquisition of I-V power supply characteristics in a way that several operating points can be easily obtained. Laboratory load current tests using ordinary power resistors are not an easy solution due to their size, cost and overall weight. To resolve that it is proposed in this paper that the current through electronically varying loads can give better resolution to the I-V characteristics of FC and PV sources. The interleaved operation of the chopper converter ensures an input high frequency current ripple, reducing so the input LC filters size and converter volume. The converter transfer function is analyzed and controllers are designed to obtain a fast dynamic response and insure good stability in steady state operation. It is presented the converter operating principles, operating states and design. The simulated and results are compared to each other in order to prove the electronic load effectiveness in acquiring the I-V biasing curves of fuel cells and photovoltaic panels.

MPPT for Magnus wind turbines based on cylinders rotation speed

This paper proposes a method to reach the maximum power point of a Magnus wind turbine. Firstly, a special discussion is made about this turbine and its behavior showing that this turbine is a special case of the horizontal axis wind generator, using rotating cylinders instead of fixed blades. Secondly, it is presented an explanation of how some maximum power point trackers (MPPT) can be used with wind energy conversion system and, specially, the divided step hill climbing search method (HCS). The MPPT method proposed for the Magnus turbine is based on the control of cylinder rotation speed to change the tip speed ratio. Finally, simulation results are presented with the proposed MPPT method applied to a Magnus wind turbine.

Electronically adjustable load for testing three phase AC systems

Some equipment such as AC voltage sources, power generators, inverters, and others converters have to be exhaustively tested before being used. To implement these tests it is necessary, in many cases, to use variable AC loads, such as passive (inductive, capacitive and resistive) and active loads (battery chargers and photovoltaic panels). This paper presents an analysis and design of an AC electronic load to emulate either purely active and reactive three-phase loads or other impedance combinations. This electronic variable load allows the user set precisely the amount of power required for practical experiments and bench tests. Furthermore, this work presents the modeling of a voltage source converter (VSC) and a buck converter, used to purpose of emulating a variable and adjustable load. Also it is discussed the compensators design to control the converter and is presented simulation results with the electronically adjustable load to active and reactive power consumption.

FC and PV emulation by buck converter based on experimental VxI curves and dynamic response

This paper presents an emulation of fuel cell and photovoltaic modules based on the buck converter as a replacement of actual power sources for bench tests. This approach is suitable for power electronic designs involving power converters to interface source and DC loads or source and mains grid, without having available the real source. The output voltage of the buck converter is referred to lookup tables/equations with experimental data from actual sources under load variation to determinate the biasing curves and dynamic response. To validate the results, a comparison between simulated and practical results obtained from laboratory test with actual sources is performed. The energy source emulations with buck converters is a simple, safe, versatile, and effective way of physically representing DC sources for various laboratory tests.

Integration of alternative sources of energy as current sources

This work proposes an integration of alternative energy sources having the different generating modules connected as current sources. These sources were configured to inject current into a common DC bus. This feature avoids current circulation among sources due to the voltage differences, reducing the stress in the individual generators. A battery bank is a system part, used as an energy accumulator for periods when there is primary energy depletion. The bus voltage is controlled by modulation of a secondary load in parallel with the main load. A DC-DC Boost converter connects each primary source to a common bus, except for the storage system that uses a DC-DC Buck-Boost converter. Finally, it is presented a mathematical analysis through simulated results to show the sources behavior and overall performance when turned into current sources.