Faete Filho

Adaptive Selective Harmonic Minimization Based on ANNs for Cascade Multilevel Inverters With Varying DC Sources

A new approach for modulation of an 11-level cascade multilevel inverter using selective harmonic elimination is presented in this paper. The dc sources feeding the multilevel inverter are considered to be varying in time, and the switching angles are adapted to the dc source variation. This method uses genetic algorithms to obtain switching angles offline for different dc source values. Then, artificial neural networks are used to determine the switching angles that correspond to the real-time values of the dc sources for each phase. This implies that each one of the dc sources of this topology can have different values at any time, but the output fundamental voltage will stay constant and the harmonic content will still meet the specifications. The modulating switching angles are updated at each cycle of the output fundamental voltage. This paper gives details on the method in addition to simulation and experimental results.

11-Level cascaded H-bridge grid-tied inverter interface with solar panels

This paper presents a single-phase 11-level (5 H-bridges) cascade multilevel DC-AC grid-tied inverter. Each inverter bridge is connected to a 200 W solar panel. OPAL-RT lab was used as the hardware in the loop (HIL) real-time control system platform where a Maximum Power Point Tracking (MPPT) algorithm was implemented based on the inverter output power to assure optimal operation of the inverter when connected to the power grid as well as a Phase Locked Loop (PLL) for phase and frequency match. A novel SPWM scheme is proposed in this paper to be used with the solar panels that can account for voltage profile fluctuations among the panels during the day. Simulation and experimental results are shown for voltage and current during synchronization mode and power transferring mode to validate the methodology for grid connection of renewable resources.

Control of cascaded H-bridge multilevel inverter with individual MPPT for grid-connected photovoltaic generators

A single-phase cascaded H-bridge multilevel inverter for a grid-connected photovoltaic (PV) system with nonactive power compensation is presented in this paper. To maximize the solar energy extraction of each PV string, an individual maximum power point tracking (MPPT) control scheme is applied, which allows the independent control of each dc-link voltage. A generalized nonactive power theory is applied to generate the nonactive current reference. Within the inverters capability, the local consumption of nonactive power is provided to realize power factor correction. A single-phase modular cascaded multilevel inverter prototype has been built. Each H-bridge is connected to a 195 W solar panel. Simulation and experimental results are presented to validate the proposed ideas.

Single-phase cascaded H-bridge multilevel inverter with nonactive power compensation for grid-connected photovoltaic generators

This paper presents a single-phase cascaded H-bridge multilevel inverter for a grid-connected photovoltaic (PV) system with nonactive power compensation. A generalized nonactive power theory is applied to generate the nonactive current reference. Within the inverters capability, nonactive power required by the local load is provided to improve the grid power quality. To minimize harmonics and achieve zero error tracking, a hybrid controller composed of a proportional controller and a repetitive controller is applied to current control. A single-phase 11-level cascaded multilevel inverter is considered in both simulation and experimental tests. Each H-bridge is connected to a 195 W solar panel. Simulation and experimental results are presented to validate the proposed ideas.

Real-time selective harmonic minimization in cascaded multilevel inverters with varying DC sources

A new approach for selective harmonic elimination in a 7-level cascaded multilevel inverter with separate DC sources will be presented. As opposed to previous research in this area, the DC sources feeding the multilevel inverter are considered to be varying in time. This method uses genetic algorithms to obtain switching angles offline for different DC source values and uses neural networks to determine the switching angles that correspond to the real-time values of the DC sources. This implies that each one of the DC sources of this topology can have different values at any time but the output fundamental voltage will stay constant and the harmonic will still meet the specifications. The paper gives details on the approach used, together with simulation and experimental results.

Real time selective harmonic minimization for multilevel inverters using genetic algorithm and artificial neural network angle generation

The work developed here proposes a methodology for calculating switching angles for varying DC sources in a multilevel cascaded H-bridges converter. In this approach the required fundamental is achieved, the lower harmonics are minimized, and the system can be implemented in real time with low memory requirements. Genetic algorithm (GA) is the stochastic search method to find the solution for the set of equations where the input voltages are the known variables and the switching angles are the unknown variables. With the dataset generated by GA, an artificial neural network (ANN) is trained to store the solutions without excessive memory storage requirements. This trained ANN then senses the voltage of each cell and produces the switching angles in order to regulate the fundamental at 120 V and eliminate or minimize the low order harmonics while operating in real time.

Hybrid single-phase multilevel inverters as renewable energy interfaces considering THD, modularity and capacitor recharging

For relatively low voltage dc sources such as photovoltaic arrays and fuel cell stacks to supply power to typical AC systems, using multilevel inverters is an approach with several advantages. In doing so, while it is possible to achieve optimal THD below 5% by staircase/block modulation of cascaded H-bridge multilevel inverters, this requires the use of several separate dc sources with different non-integer ratio values. This paper proposes having some of these source values be equal to each other to increase sub-system modularity, and replacing some H-bridge cells by a diode-clamped inverter to reduce the required number of separate dc sources, while still achieving near-optimal THD below 5%. In addition, a means of re-charging the diode-clamped inverters inner capacitors is proposed Analytical, simulation and experimental results are presented for an example hybrid converter with four H-bridge cells in series with a 5-level diode-clamped inverter.

Multilevel cascade h-bridge inverter dc voltage estimation through output voltage sensing

This work presents an approach to determine the input voltage value of each cell in a cascade H-bridge multilevel inverter using a sensor at the output of the inverter to eliminate all the dc voltage sensors measuring the individual source voltages. The input voltages can be equal or unequal. The MOSFET device datasheet, the ambient temperature, and the modulation strategy are utilized to estimate the switch voltage drop to compensate for the measurement. The output voltage is then processed by a DSP unit that uses the signals that command the switches to estimate the voltage at each cell. Simulation and experimental results are shown for a seven-level cascade multilevel inverter operating under a RLC load.

Quantitative performance characterization of multilevel PWM techniques in high power medium voltage three-level NPC-based industrial drives

In this paper, four multilevel pulse-width-modulation methods are quantitatively characterized and compared: phase opposition disposition (POD), Space vector modulation with switching loss minimization (SVPWM-SLM), and selective harmonic elimination (SHE) of non-triplen harmonics up to the 15th and 27th harmonics, respectively. Inverter losses and efficiency, induction machine voltage, and current harmonics are analyzed. Analytical and simulation results using PLECS and MATLAB/Simulink for control systems are experimentally verified with a 1000-hp 4160-V neutral-point-clamped (NPC) adjustable-speed-drive (ASD) system.