50 research outputs found
Optimal Scheduling of Energy Storage Using A New Priority-Based Smart Grid Control Method
This paper presents a method to optimally use an energy storage system (such as a battery)
on a microgrid with load and photovoltaic generation. The purpose of the method is to employ the
photovoltaic generation and energy storage systems to reduce the main grid bill, which includes
an energy cost and a power peak cost. The method predicts the loads and generation power of
each day, and then searches for an optimal storage behavior plan for the energy storage system
according to these predictions. However, this plan is not followed in an open-loop control structure
as in previous publications, but provided to a real-time decision algorithm, which also considers
real power measures. This algorithm considers a series of device priorities in addition to the storage
plan, which makes it robust enough to comply with unpredicted situations. The whole proposed
method is implemented on a real-hardware test bench, with its different steps being distributed
between a personal computer and a programmable logic controller according to their time scale.
When compared to a different state-of-the-art method, the proposed method is concluded to better
adjust the energy storage system usage to the photovoltaic generation and general consumption.Unión Europea ID 100205Unión Europea ID 26937
New space vector modulation algorithms applied to multilevel converters with balanced DC-link voltage
This work presents a survey of new space vector modulation algorithms for high power voltage source multilevel converters. These techniques provide the nearest switching vectors sequence to the reference vector and calculates the on-state durations of the respective switching state vectors without involving trigonometric functions, look-up tables or coordinate system transformations which increase the computational load corresponding to the modulation of a multilevel converter. These algorithms drastically reduce the computational load maintained permitting the on-line computation of the switching sequence and the on-state durations of the respective switching state vectors. The on-state durations are reduced to a simple addition. In addition, the low computational cost of the proposed methods is always the same and it is independent of the number of levels of the converter. The algorithms have been satisfactorily implemented in very low-cost microcontrollers.Ministerio de Ciencia y Tecnología DPI 2001-308
Adaptive Vectorial Filter for Grid Synchronization of Power Converters Under Unbalanced and/or Distorted Grid Conditions
This paper presents a new synchronization scheme for detecting multiple positive-/negative-sequence frequency harmonics in three-phase systems for grid-connected power converters. The proposed technique is called MAVF-FLL because it is based on the use of multiple adaptive vectorial filters (AVFs) working together inside a harmonic decoupling network, resting on a frequency-locked loop (FLL) which makes the system frequency adaptive. The method uses the vectorial properties of the three-phase input signal in the αβ reference frame in order to obtain the different harmonic components. The MAVF-FLL is fully designed and analyzed, addressing the tuning procedure in order to obtain the desired and predefined performance. The proposed algorithm is evaluated by both simulation and experimental results, demonstrating its ability to perform as required for detecting different harmonic components under a highly unbalanced and distorted input grid voltage
A Neural Controller for quasi-resonant converters
A neural controller implementing an energy feedback control law is proposed to improve
the stability and dynamic characteristics of the series resonant converter (SRC). The cnert)' feedback
control is introduced and analysed in discrete time domain. A novel formulation of the control law
is suggested. The adaptive control law is learnt by an analog neural network (ANN). An easy imple·
mentation of this controller is proposed and applied to a SRC circuit. Simulation results show a good
improvement in the SRC response and confirm the validity of the controller
DC-Voltage-Ratio Control Strategy for Multilevel Cascaded Converters Fed With a Single DC Source
Recently, a multilevel cascaded converter fed with a single DC source has been presented. An analysis of the steady-state working limits of this type of converter is presented in this paper. Limits of the maximum output voltage and the minimum and maximum loading conditions for stable operation of the converter are addressed. In this paper, a way to achieve any DC voltage ratio (inside the stable operation area of the converter) between the H-bridges of the single-DC-source cascaded H-bridge converter is presented. The proposed DC-voltage-ratio control is based on a time-domain modulation strategy that avoids the use of inappropriate states to achieve the DC-voltage-ratio control. The proposed technique is a feedforward-modulation technique which takes into account the actual DC voltage of each H-bridge of the converter, leading to output waveforms with low distortion. In this way, the dc voltage of the floating H-bridge can be controlled while the output voltage has low distortion independently of the desired DC voltage ratio. Experimental results from a two-cell cascaded converter are presented in order to validate the proposed DC-voltage-ratio control strategy and the introduced concepts.Ministerio de Ciencia y Tecnología TEC2006-03863Junta de Andalucía EXC/2005/TIC-117
Analysis of the power balance In the cells of a multilevel cascaded H-Bridge converter
Multilevel cascaded H-Bridge converters (CHB)
have been presented as a good solution for high power applications.
In this way, several control and modulation techniques
have been proposed for this power converter topology. In this
paper the steady state power balance in the cells of the single
phase two cell CHB is studied. The capability to be supplied with
active power from the grid or to deliver active power to the grid
in each cell is analyzed according to the dc-link voltages and
the desired ac output voltage value. Limits of the maximum and
minimum input active power for stable operation of the CHB are
addressed. Simulation results are shown to validate the presented
analysis
Predictive middle point modulation: a new modulation method for parallel active filters
When designing an Active filter, using a current-controlled voltage source inverter, there are two main tasks : to generate an appropiate reference, for nulling harmonic current and reactive power, ant, on the other side, to generate a switching pattern that permits to follow the reference as close as it can be done. Predictive Middle Point Modulation (PMPM) is a novel modulation technique, specially suited for Active Filters. This method is derived from predictive Dead-Beat controller, improving its dynamic response and current error. Simulation results confirm the validity of the proposed method. Experimental results will be provided in the final paper
Effective modulation algorithm for three-level converters
This paper presents an effective modulation algorithm (EMA) for high power voltage source three-level converter. This approach drastically reduces the computational load maintained, being substituted by decision making. This method permits the on-line computation of the switching sequence and the on-state durations of the respective switching state vectors corresponding to the modulation of a three-level inverter. Therefore stored information from a memory or a table is not necessary in EMA. The modulation method used in this work presents the advantage of eliminating the angle from the calculations. This modulation technique permits an economic and simply electronic implementation
Feed-forward Space Vector Modulation for Single-Phase Multilevel Cascade Converters with any DC voltage ratio
Modulation techniques for multilevel converters
can create distorted output voltages and currents if the DC link
voltages are unbalanced. This situation can be avoided if the
instantaneous DC voltage error is not taken into account in the
modulation process. This paper proposes a feed-forward space
vector modulation method for a single-phase multilevel cascade
converter. Using this modulation technique, the modulated output
voltage of the power converter always generates the reference
determined by the controller even in worst case voltage unbalance
conditions. In addition the possibility of optimizing the DC
voltage ratio between the H-bridges of the power converter is
introduced. Experimental results from a 5kVA prototype are
presented in order to validate the proposed modulation technique
Conventional Space-Vector Modulation Techniques versus the Single-Phase Modulator for Multilevel Converters
Space-vector modulation is a well-suited technique
to be applied to multilevel converters and is an important
research focus in the last 25 years. Recently, a single-phase
multilevel modulator has been introduced showing its conceptual
simplicity and its very low computational cost. In this paper,
some of the most conventional multilevel space-vector modulation
techniques have been chosen to compare their results with those
obtained with single-phase multilevel modulators. The obtained
results demonstrate that the single-phase multilevel modulators
applied to each phase are equivalent with the chosen wellknown
multilevel space-vector modulation techniques. In this
way, single-phase multilevel modulators can be applied to a
converter with any number of levels and phases avoiding the
use of conceptually and mathematically complex space-vector
modulation strategies. Analytical calculations and experimental
results are shown validating the proposed concepts