Miguel Pablo Aguirre

Multilevel Current-Source Inverter With FPGA Control

In this paper, a multilevel current-source inverter (MCSI) topology is analyzed. The issue of constructing a novel modular single-rating inductor MCSI is explored, taking advantage of the features of field-programmable gate arrays (FPGA) for control and gate signal generation. The proposed topology is built with identical modules where all inductors carry the same amount of current, simplifying the construction and operation of industrial applications with higher efficiency. A new state-machine approach, which is easy to implement in an FPGA, and a proper implementation of the phase-shifted carrier sinusoidal pulse width modulation (PSC-SPWM) allow both current balance in all modules and effective switching-frequency minimization. The performance of the MSCI proposed is simulated with Matlab and is verified by constructing a prototype.

Single-Stage Fuel Cell to Grid Interface With Multilevel Current-Source Inverters

Renewable energy sources can be used for electric power generation to supply specific devices in distributed systems such as smart grids. Hydrogen fuel cells have proven to be an effective solution to produce electrical energy with fairly good efficiency and minimum environmental pollution. A single-stage solution to interconnect a fuel cell with a low-voltage distribution system is proposed in this paper. The traditional boost dc/dc converter plus voltage source inverter is replaced by a single-stage multilevel current-source inverter (MCSI). The MCSI can both interconnect to the grid and perform the maximum power point tracking algorithm. This novel single-stage converter approach provides active power to the grid, power factor compensation, and reduction of the line current harmonic content. The synchronization, modulation, and control scheme are implemented on a field-programmable gate array board using a fast-prototype high-level synthesis tool to reduce design time. Both simulation and experimental results show excellent behavior and fast dynamics while complying with IEEE and IEC harmonic content regulations.

High speed fixed point DSOGI PLL implementation on FPGA for synchronization of grid connected power converters

Power converters are the subject of extensive research because of their ability to work under different operating conditions, providing bidirectional power flow, high dynamic range and fast response. These advantages allow them to be used as an interface between the electric grid and many high power applications such as motors, energy storage, active filters and renewable energy sources. To be able to connect to the utility grid, every power converter must be provided with a synchronization method. The synchronization algorithms are mostly based on the well known Synchronous Reference Frame Phase Locked Loop (SRF-PLL) plus some pre-filter stage that can be achieved by different algorithms of variable complexity, usually implemented on Digital Signal Procesors (DSP) or Microcontrollers. In this paper a simple and highly effective Field Programable Gate Array (FPGA) implementation of a Phase Locked Loop (PLL) algorithm based on a Dual Second Order Generalized Integrator PLL (DSOGI-PLL) is presented in detail, along with the auxiliary circuitry needed to acquire the grid voltage information. Using a fast-prototype high-level synthesis tool, design time is drastically reduced without the need of any Hardware Description Language (HDL) code. Both simulation with MATLAB Simulink and experimental results on a Xilinx FPGA, show a robust behaviour even against frequency steps, severe distortion and unbalances in the power input.

Multilevel current source inverter to improve power quality in a distribution network

This paper deals with the problem of reactive power and harmonics in a standard medium voltage (MV) distribution network. It presents the design of a shunt active filter implemented with a multilevel current source inverter (MCSI) connected to the medium voltage level of a power distribution system. The proposed MCSI is made by identical modules where all inductors carry the same amount of current. The current balance is achieved by a Phase-Shifted Carrier SPWM proper implementation. The performance of proposed active filter is thoroughly simulated with Matlab Simulink. It shows very good behavior in steady state and transient conditions.

Current balance control in a multilevel current source inverter

Multilevel converters constitute a high performance and high reliability option for industrial applications such as motor control, transmission and distribution electrical systems, and interface with alternative energy sources and non-conventional storage systems. The biggest challenge about multilevel topologies is the balance of dividing reactive components (capacitors in voltage converters, and inductors in current converters). In this paper, two methods to force current balance in a Multilevel Current Source Inverter (MCSI) are presented. Both require minimum computing power with excellent closed loop dynamic response.

High speed single phase SOGI-PLL with high resolution implementation on an FPGA

Every power converter needs a precise synchronization method to be able to connect to the utility grid. The synchronization impacts directly on the performance of the converter. Synchronization algorithms are often based on the well known Synchronous Reference Frame Phase Locked Loop (SRF-PLL). These are usually implemented in software on Digital signal Processors (DSP) or Microcontrollers and the maximum sample rate that can be achieved is limited by the hardware used. In this paper a simple and highly effective Field Programmable Gate Array (FPGA) implementation of a Phase Locked Loop (PLL) algorithm based on a Second Order Generalized Integrator PLL (SOGI-PLL) with a high sampling frequency of 500 kHz and 16 bit resolution is presented in detail. Design time is drastically reduced by the use of a fast-prototype high-level synthesis tool without the need of any Hardware Description Language (HDL) code. Both simulation and experimental results on a Xilinx FPGA show an excellent behavior even against severe distortion and frequency or phase steps in the input voltage.

An example of rapid design of power electronics control with FPGA in Matlab/Simulink

This paper deals with the problem of the design of an all-digital implementation of a three-phase PLL and the control logic of a shunt active filter implemented with a Multilevel Current Source Inverter (MCSI). The active filter is connected to the medium voltage level of a power distribution system where compensation of reactive power and harmonics is mandatory. The PLL is essential to obtain a reference frame for grid synchronization. The performance of proposed PLL structure and logic control is simulated via Matlab/Simulink. The proposed PLL structure shows fast synchronization and adequate tolerance to grid voltage unbalance. Both the PLL and the control logic can be downloaded and tested on a Field-Programmable-Gate-Array (FPGA) using the same software tool.

Experimental implementation of an electronic load for global maximum power point tracking

This work deals with the partial shading effect in the power curve of a PV solar array. Using a semiconductor device — MOSFET or IGBT — as electronic load added to a buck converter, it is possible to scan the power curve of a photovoltaic string and therefore empirically determine its optimum voltage, even in presence of partial shading. The aim of this paper is to give experimental details regarding the laboratory implementation of a proof-of-concept prototype meant to detect the Global Maximum Power Point. Three cases are presented that consider the partial shading effect of a PV string, with disturbances of different sizes and shapes. In the last part a novel exciting signal is presented, which allows to reduce the scanning time of the power curve. The experimental results illustrate the performance of the implemented circuit.

A novel modulation technique for single phase current source inverters with Active Buffering

Interface between electric grids and renewable energy sources are of a big concern to researchers worldwide. Many efforts are applied to obtain converter topologies and modulation techniques with increasing features regarding switching behavior, input and output distortion, efficiency, switches utilization ratio and reliability. Interfacing constant power sources with sinusoidal systems require huge storage capabilities to compensate the oscillating output power. This storage implies higher costs, lower reliability and bulkier systems. In this paper a new modulation technique for a single phase Current Source Inverter (CSI) with an Active Buffer (AB) is presented. The AB allows to reduce the size and ripple requirements of the storage element, increasing reliability and improving overall performance.

Control System to Balance Internal Currents of a Multilevel Current-Source Inverter

Multilevel current-source inverters have proved to be a high-performance option for industrial applications due to reliability, fault-tolerant capabilities, quasi soft switching, and the use of lower filter capacitor values. One of its major challenges is to balance the internal currents that feed each module. Imbalances could be caused by manufacturing deviations of the reactive components, temperature drift or aging, nonlinear loads, and modulation errors, among others. Using the well-known phase-shift carrier sinusoidal pulse width modulation, a slight change in the amplitude of the carrier signals produces a variation in the average value of the internal currents. In this paper, we introduce a control strategy to balance the current of the inductors and its implementation in a prototype. Simulation and experimental results at different operating conditions show a robust behavior of the control system along with a low distortion in the output voltages and currents of the converter.