This paper presents the detailed project of a modular educational kit to be used in research and teaching activities in the area of power electronics -with emphasis on applications in medium voltage multilevel converters. The half bridge topology has been chosen for the submodules, as they can be arranged together in a multitude of other topologies. A system composed by a mother board and daughter cards is presented. A DSP control card and a FPGA System-On-Module are inserted in the mother board in order to control the half bridge submodules. The targets of this project are applications in medium voltage -hence, the communication between the submodules and the FPGA/DSP is performed through optical fibers. Also a self power system is presented for the submodules, in order for them to operate at floating potentials. Experimental results have been presented for the most usual topologies of converters, including a Modular Multilevel Converter operating at 2000V.
This paper presents the development of a peak-shaving equipment, composed by a multilevel converter in a cascaded H-bridge topology and battery banks on the DC links. Between specific time periods, when the demand is higher, the equipment injects active power from the batteries into the grid to provide support to the system. During the other times of the day, when the demand is lower, the converter charges its battery banks with the exceeding (and low producing cost) energy from the grid. The charge and discharge control algorithms are implemented in a digital signal processor (DSP). The precise time of the day information is obtained from a real-time-clock from a global positioning system module (GPS), which communicates with the DSP through the serial interface. This paper presents the control algorithms and experimental results obtained in a 24 h continuous operation of the equipment.
This paper presents the development and operation on 13.8kV distribution systems of a peak-shaving equipment with battery energy storage. This equipment injects active power to grid during peak times (when the cost of energy is higher) and charges its battery banks from the grid at the off-peak times (when the energy has a low producing cost). The equipment is based on a multilevel converter coupled to the grid through a 2.4kV:13.8kV transformer. In addition to the peak-shaving functionality, a feature of compensation of harmonics on the distribution voltage is included, without the need for any extra sensor nor hardware (apart from the ones already in use for the peak-shaving). The compensation of voltage harmonics is performed through the emulation of a harmonic resistance in order to damp resonances between system impedances that are excited by non-linear loads. This approach is very appealing to distribution systems, where the non-linear loads are not accessible and are scattered. Experimental results obtained on a 13.8kV test substation are presented.
The city of Aripuana is one of the largest wood producer in the state of Mato Grosso, Brazil. Wood residues are used in the electricity generation at three thermoelectric plants in this region. However, the plants have high costs in transporting the wood residues (due to poor road conditions). Hence, this paper compares the energy performance of wood residues in natura and compacted as briquettes by calculating the heating value and determining the influence of moisture content on the energy characteristics of wood residues. The goal is to demonstrate the viability of using briquettes in order to improve thermoelectric generation. The wood residues from this region are affected by the high humidity of the biome. An alternative to improve the use of energy contained in the wood residues is to produce briquettes with lower humidity. This allows one to maintain high levels of heat energy in a lower volume, facilitating handling and storage. The results show that the use of briquettes improved the performance of thermoelectric plants, generating 1 MW of electricity power with less than 1 ton of briquettes. This contributes to the preservation of the environment, reducing operating costs, transportation and storage of the raw materials.
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