Adriana Florescu

The advantages, limitations and disadvantages of Z-source inverter

A Z-source converter is an unique x-shaped impedance network called Z-source impedance network that couples the converter main circuit to the power source. The converter may be of all conversion types - if it is of ac-to-dc type, the z-source converter is called z-source inverter. Since 2003 when this recently conversion concept appeared [1], it proved able to solve many conversion problems. In this paper its superiority compared to traditional solutions are shown. There are also small disadvantages and limitations revealed.

Single-phase active power filter with improved sliding mode control

This paper presents a study about a single-phase shunt active power filter with sliding mode control. The operation mode of the shunt active filter is detailed, introducing a new operating mode for the inverter in order to improve the behavior of the line current during the zero-passings. Regarding sliding mode control, the sliding surface, the existence condition and the equivalent control are analysed. The steady-state error is diminished by implementing a proposed sliding surface, which includes the current error and its integral. The expected results are confirmed through simulation.

The analysis of the solutions for harmonic elimination PWM bipolar waveform with a specialized differential evolution algorithm

The selective harmonic elimination pulse-width modulation (SHE-PWM) offers multiple solutions depending of the number of switching angles or problem formulation, each one with different harmonic performance. This paper proposes a novel approach to the SHE-PWM problem, using a minimization technique based on a specialized evolutionary algorithm that can find all solutions for a given modulation index. The algorithm, based on the Differential Evolution (DE), is tested on the bipolar waveform with quarter-wave symmetry for three-phase inverters. In order to provide a complete analysis of the solutions, four performance indicators are used: a harmonic distortion factor that takes into account the first two (HDF2) and the first four (HDF4) significant harmonics, the total harmonic distortion (THD) and weighted THD (WTHD) of the output line voltage. The distribution of the switching angles in the first quarter-period is also analyzed and a general formulation that allows the identification of the best solution from the ones found for N switching angles is proposed.

Microcontroller-based Walsh function PWM modulation with harmonic injection technique

An improved pulse width modulation (PWM) method for three-phase inverters using the Walsh function harmonic elimination method with harmonic injection technique is presented, together with a noniterative algorithm that produces a set of linear equations that relates switching angles with the output phase voltage fundamental. The approach used gives a set of solutions with a near-linear trajectory which can be approximated by straight-line curve fitting. Thus, on-line control of fundamental amplitude and frequency is possible with a microcontroller-based implementation. The novel use of harmonic injection technique maximizes the output line voltage fundamental. The theoretical predictions are confirmed by computer simulation and DSC-based hardware implementation.

Matching the performances of a Diesel engine with a mild-hybrid driving system, based on telemetry data

Because current regulations stimulate engine downsizing, achieving high performances with a small displacement engine is very difficult, keeping in the same time the level of emissions and fuel consumption as low as possible. This article aims to provide a solution for these challenges, combining a small displacement turbocharged Diesel engine with an Axial Flux Permanent Magnet (AFPM) electric motor, in a plug-in parallel mild-hybrid powertrain, yet delivering the same dynamic performances of a larger displacement and more powerful engine, with the advantages of both, meaning reduced emissions and fuel consumption, with no compromise regarding the power output. All the data provided in this article are based on measurements performed in real road driving conditions and cover many possible scenarios and situations, such as heavy accelerations, traffic jams, uphills and downhills, overtaking and engine braking, during various weather conditions.

Design optimization methods of an intelligent controller from a speed control system

The paper presents fuzzy logic simple and combined with evolution strategies and neuro-fuzzy designs of a duty-cycle compensation controller in order to linearize the nonlinear external characteristics family of a step-down or forward DC-DC converter that supplies DC motors. The controller is additionally introduced in high precision speed control systems. Comparisons between classical PI controllers and fuzzy controllers are made. Advantages of combined methods of computational intelligence domain are revealed.

Simple power management control for a plugin mild-hybrid Diesel powertrain

The number of Diesel powered cars has increased in the last decade, which leaded to the intensifying of air pollution, especially inside big cities, mostly due to NOx emissions. Instead of banning these engines, an alternative is to develop a smart Power Management Control (PMC), suitable for Plug-In Hybrid Electric Vehicles (PHEVs), as this paper proposes, where a small displacement Diesel engine is combined with a compact Axial Flux Permanent Magnet (AFPM) electric motor, yet capable to match the performances of a larger displacement engine. Besides the benefit of reduced CO2 and NOx emissions, this configuration also leads to improved fuel economy, the car being able to run in full Electric Vehicle (EV) mode at low cruising speeds. In order to have a good estimation on the total energy consumption, the key parameters of the driving system (DS) were chosen based on real road driving measurements.

Power Conversion and Energy Management for Mission-Critical Systems

The need for high power density has been the trend of the power conversion industry for many years. The key to obtain a high power density is to increase system’s efficiency. In the case of space applications, there is the same need for high power density but with the very important note that the reliability of the system must not be compromised. In order to increase system’s efficiency while maintaining reliability, the latest soft switching converter topologies, high power density packaging, improved heat extraction and planar magnetics are used. Other key parameters are: the digital loop control and the digital energy management through microcontrollers, and digital signal controllers.

Power Architectures and Power Conditioning Unit for Very Small Satellites

Space agencies all over the world are interested today in very small satellites because of their advantages compared to heavier satellites. This chapter starts with the general characteristics, Earth orbits, eclipses and current missions of very small satellites. It continues with a brief summary of the component parts of the electrical power system: the array of solar cells, batteries for space applications, 3 power architectures and 19 maximum power point tracker’s algorithms. Authors’ attention is mainly focused on designing, simulation and practical demonstration of a prototype with a flexible hybrid proposed architecture of the power conditioning unit for very small satellites, whose component blocks are the battery charge unit (BCU) including the dc–dc converter, the digital controller, the BCU sensors circuitry and the BCU prototype) and the battery charge/discharge monitor unit (BCDMU) including the microcontroller, the BCDMU sensors circuitry, the battery switch, the battery heater and the telemetry system.

Implementation of frequency-modulated triangular carrier and slope PWM strategies for three-level NPC inverters

Multilevel inverters produce an output voltage with superior quality compared to the voltage obtained by two-level converters. They are controlled with pulse width modulation (PWM) methods and have a limited switching frequency due to semiconductor devices switching losses. This paper presents the implementation for multilevel converters of two generated PWM methods that were previously proposed for two level converters. The considered methods, sinusoidal carrier regulated by the slope of a trapezoidal waveform PWM (SLPWM) and frequency modulated triangular carrier PWM (HIPWM-FMTC), control the output voltage spectrum while keeping the number of commutations low for a given fundamental frequency.