P.F. Donoso-Garcia

A three-phase line-interactive UPS system implementation with series-parallel active power-line conditioning capabilities

This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with series-parallel active power-line conditioning capabilities, using a synchronous reference frame (SRF) based controller, which allows an effective power factor correction, load harmonic current suppression and output voltage regulation. The three-phase UPS system is composed of two active power filter topologies. The first one is a series active power filter, which works as a sinusoidal current source in phase with the input voltage. The other is a parallel active power filter, which works as a sinusoidal voltage source in phase with the input voltage, providing to the load a regulated and sinusoidal voltage with low total harmonic distortion (THD). Operation of a three-phase phase-locked loop (PLL) structure, used in the proposed line-interactive UPS implementation, is presented and experimentally verified under distorted utility conditions. The control algorithm using SRF method and the active power flow through the UPS system are described and analytically studied. Design procedures, digital simulations and experimental results for a prototype are presented to verify the good performance of the proposed three-phase line-interactive UPS system.

A space vector PWM method for three-level voltage source inverters

In this paper, a space vector PWM method for three-level inverters is presented. In the proposed technique, boundary restrictions can be easily incorporated to the harmonic distortion output voltages, to limit the minimum pulse width and to balance the voltages of the dc-link capacitor bank. The solutions obtained are simple algebraic equations relating directly the pulse widths of the gate signals to the phase reference voltages. Computer simulation results are used to demonstrate the main features of the proposed technique.

A comparative analysis of control algorithms for three-phase line-interactive UPS systems with series-parallel active power-line conditioning using SRF method

This paper presents alternative control algorithms using synchronous reference frame (SRF) based controllers, which allow an effective power factor correction, load harmonic current suppression and output voltage regulation for three-phase line-interactive UPS systems with active series-parallel power-line conditioning capability. The proposed UPS systems are composed of two active power filter topologies. The first one works as a series active power filter and the other works as a parallel active power filter. An analysis of two control algorithms using SRF method, including compensation of the instantaneous real input power is carried out. The control algorithms are described, and next analytically studied to verify their characteristics. Digital simulations are presented to confirm their good performance.

A three-phase series-parallel compensated line-interactive UPS system with sinusoidal input current and sinusoidal output voltage

This paper deals with a three-phase line-interactive uninterruptible power supply system with active series-parallel power-line conditioning capability, which has sinusoidal output voltage regulation capability and unity power factor. In this system, two active power filter topologies are applied. The first one is a series active power filter which can compensate supply voltage harmonics and voltage unbalances as well. The other is a parallel active power filter which has the following main goals: reactive power compensation; load current harmonics suppression; and battery bank charging during normal power supply conditions. During input power failure, the parallel filter maintains uninterruptible power for critical loads, delivering power from the battery bank without power interruption, ensuring sinusoidal output voltages with constant RMS voltage value and low total harmonic distortion (THD). Therefore the proposed line-interactive UPS has low THD sinusoidal input currents with unity power factor. The control algorithm and mathematical models of the proposed three-phase line-interactive UPS system are described, and digital simulations are presented to verify the good dynamic responses of the versatile scheme.

Acoustic Resonance Avoidance in High Pressure Sodium Lamps Via Third Harmonic Injection in a PWM Inverter-Based Electronic Ballast

Third harmonic injection in the high pressure sodium lamp voltage by means of a controlled pulsewidth modulation inverter is studied in this paper. It can be shown that acoustic resonance can be avoided by using this technique with a judicious amount of third harmonic injection. Furthermore, the crest factor in the lamp current can also be reduced

Distributed Secondary Level Control for Energy Storage Management in DC Microgrids

DC microgrids have been known to be a promising solution for improving renewable energy integration with electrical grid and enhancing the system’s overall energy efficiency. A key component of this microgrid is the energy storage system, which besides smoothing the intermittent behavior of renewable sources, also allows intentional islanding and the execution of optimization routines to improve the microgrid performance. Assuming that storage systems in commercial and residential buildings will mostly be composed of multiple storage units, an energy storage management system, which provides charge/discharge monitoring and state-of-charge (SOC) equalization, is needed to prevent overcharging the units or their uneven use, which can lead to faster deterioration of battery banks. This paper proposes an energy storage management system based on distributed secondary level control, which promotes charge/discharge control and provides SOC equalization simultaneously. The SOC imbalance compensation alters the energy storage unit virtual droop resistance according to the difference between the unit SOC and the microgrid average SOC, thus the compensation intensity is dependent on the imbalance level being suitable to be employed in dc bus signaling controlled microgrids.

Comparative analysis of power LEDs dimming methods

Light emitting diodes (LEDs) have many features that make them very attractive for use in lighting. The main features that stand out is its small size compared to incandescent and fluorescent lamps. Also, they have high luminous efficiency, long lifetime and are resistant to shocks and vibrations, which contributes to increasing their reliability. This paper presents a current source for Power LEDs. As the luminous intensity of LEDs is directly related to the direct current flowing through them, this source must have characteristics of current source. Two methods of dimming LEDs are analyzed: continuous variation of current and pulse width modulation (PWM). These methods are implemented, tested and compared. A current loop to control the current through the LEDs is designed to keep the current in the LEDs always constant, so that the luminous flux emitted by them does not change.

Comparison of MPPT approaches in autonomous photovoltaic energy supply system using DSP

This paper presents a methodology for choosing the most suitable Maximum Power Point Tracking - MPPT for charging the batteries of an autonomous photovoltaic energy supply system. Experimental results are provided.

Electronic Ballast for High Pressure Sodium Lamps without Acoustic Resonance via Controlled Harmonic Injection Synthesized with PWM

This paper presents a study and analysis of a electronic ballast for high pressure sodium lamps followed by simulation and experimental results. The acoustic resonance control technique consists in the injection of current harmonics fed to the lamp, which are synthesized by the full bridge inverter via PWM through an LC filter. The controlled harmonic spectrum of current supplied has been used in order to avoid acoustic resonance. Another interesting feature of this approach is the reduction of the crest factor of the lamp current. Acoustic resonance happens when the inverter is operating in high frequency, which has certain advantages as the use of smaller and less costly passive elements, although the switching losses increase and acoustic resonance may occur. The use of currents with harmonics is a way of avoiding the excitation of this resonance due to the frequency spread. The LC filter design is also presented, which allows the desired harmonics to pass with controlled amplitudes, while filtering undesired high frequency components. Furthermore, simulation and experimental results of the proposed electronic ballast are presented to verify the analytical discussions and the design specifications

Study of the application of bidirectional dual active bridge converters in dc nanogrid energy storage systems

This paper discusses the application of a dual active bridge converter (DAB) as a bidirectional interface between the energy storage system and the main dc bus in a dc nanogrid. A novel control technique based on control loops competition is proposed to perform the energy management between both systems, which allows the dual active bridge to concomitantly regulate the main dc bus and control the battery bank charging process with a four states method.