Modeling and controller design of quasi-Z-Source inverter with battery based photovoltaic power system

A Photovoltaic (PV) power generation system based on quasi-Z-Source inverter (qZSI) with energy storage is presented. A dynamic small-signal model of qZSI with battery is established. Further, the battery power and current double-loop controllers are designed to manage the battery state of charge (SOC). Meanwhile, an improved PQ decoupling control is achieved to smooth the grid-injected power. The obtained simulation and experimental results certify the validity of the proposed control schemes, which provides an efficient method for future energy-storage PV power generation systems

Förhandlingar om kulturföremål. Parters intressen och argument i processer om återförande av kulturföremål

Disputes over demands for a return of cultural objects, in many cases museum objects, are well known. But such conflicts can also be seen as negotiations, which can be analyzed as well. This thesis adds a negotiation perspective and by a close scrutiny points out certain factors and arguments which can facilitate a process, cause a blocking, or rescind a blocking. By referring to such a process as a form of negotiation, this might bring about possibilities for the parties involved, which they otherwise would not been considering. It may occur that behind a party's arguments some interests could have been hidden consciously, or been surpassed by something else, which can cause a blocking. The aim of this thesis is to highlight the actors' different perspectives in negotiations concerning return of cultural objects, how they argue in a negotiation position and how the process can affect the management of cultural objects. The negotiation perspective can generate knowledge for increased understanding of motives behind the parties' positions. The specific traits of negotiation processes and what arguments and interests that may be important during the passage of events are examined in two case studies. One case is about the process of the return of medieval ecclesiastical objects from a museum context to two rural churches on Gotland, Sweden. The other study examines the process of negotiating the return of a totem pole from the Museum of Ethnography in Stockholm to the people of Haisla First Nation, Canada. The material that has been analyzed in this thesis shows in which phase in the process and why the parties changed their opinion, thus making a constructive solution possible. The thesis identifies aspects that the parties considered important in the negotiation process, and the outcome indicates how essential factors are valued in cases where the return of cultural objects are negotiated. Values and arguments, present in the case studies, are identified and categorized, which then are compiled into tables in order to make them comparable. These tables show in what period turning points took place in the process, and which aspects made parties change their respective standpoint, as the situation shifted from disagreement to consensus. For instance, groups of arguments that associates to the categories are: place, cultural identity, conservation and economy, are strong indicators of what some people find important. This thesis shows why and how the parties were convinced of the benefits of a solution grounded in consensus. By using a negotiation perspective the analysis identifies incentives that created a progressive process. The findings are useful for better understanding of future processes of returning cultural objects and benefit the development of the management of cultural heritage

Diagnosis of Stator Turn-to-Turn Fault and Stator Voltage Unbalance Fault Using ANFIS

An induction machine is a highly non-linear system that poses a great challenge because of its fault diagnosis due to the processing of large and complex data. The fault in an induction machine can lead to excessive downtimes that can lead to huge losses in terms of maintenance and production. This paper discusses the diagnosis of stator winding faults, which is one of the common faults in an induction machine. Several diagnostics techniques have been presented in the literature. Fault detection using traditional analytical methods are not always possible as this requires prior knowledge of the exact motor model. The motor models are also susceptible to inaccuracy due to parameter variations. This paper presents Adaptive Neuro-fuzzy Inference system (ANFIS) based fault diagnosis of induction motors. The distinction between the stator winding fault and supply unbalance is addressed in this paper. Experimental data is collected by shorting the turns of a health motor as well as creating unbalance in the stator voltage. The data is processed and fed to an ANFIS classifier that accurately identifies the faulted condition and unbalanced supply voltage conditions. The ANFIS provides almost 99% accurate and computationally efficient output in diagnosing the faults and unbalance conditions.DOI:http://dx.doi.org/10.11591/ijece.v3i1.185

Finite control set model predictive control for grid-tied quasi-Z-source based multilevel inverter

In this paper, a finite control set Model Predictive Control (MPC) for grid-tie quasi-Z-Source (qZS) based multilevel inverter is proposed. The proposed Power Conditioning System (PCS) consists of a single-phase 2-cell Cascaded H-Bridge (CHB) inverter where each module is fed by a qZS network. The aim of the proposed control technique is to achieve grid-tie current injection, low Total Harmonic Distortion (THD) current, unity power factor, while balancing DC-link voltage for all qZS-CHB inverter modules. The feasibility of this strategy is validated by simulation using Matlab/Simulink environment

Novel Control Algorithm for control of qZSI as Front - End Converter during nonsunlight hours

Degrading effect of energy generation from fossil fuel are extensively discussed and debated leading to paradigm shift to renewable energy generation. Energy generation from PV panels is the best alternative for state of Qatar which gets abundant sunlight throughout the year. Development of energy generation from PV panels helps in achieving the notion of "Energy Security". Energy security refers to availability of reliable, cheap and quality power for consumption from customer point of view. Development in power electronics helps in achieving this idea by developing and operating converters circuits with good efficiency, efficacy, reliable, robust and free from maintenance. Encouraging the nurture and development of local energy suppliers will help in minimizing the cost of installation and maintenance. Including these economic constraints in the design of converters has become a crucial factor in developing industry oriented products through academic research. Suitability of several power converters for synchronizing the power generated from PV panels to utility grid. Recently developed Impedance source based converters are highly suitable for synchronizing the power generated from renewable energy to the utility grid. They eliminate the need for extra dc-dc converter by boosting the input voltage supplied from PV panels. Impedance source based converters are categorized as: Z Source Inverter and quasi Z Source Inverter (qZSI). qZSI is preferred due to its higher performance and continuous input current. Several methods are discussed in the literature to achieve boosting of input voltage. Inverter control requires modification in conventional Sine-Triangle compared based PWM. Operation of qZSI at different MPPT algorithms is also discussed. Cascaded qZSI operation to achieve higher power rating are also discussed. Implementation of advanced control techniques such as Model predictive control is also presented. Energy efficient qZSI achieved through different methods are also discussed. This paper presents novel control algorithm for control of qZSI as Front-End Converter (FEC) during non-sunshine hours. During sunshine hours, qZSI is controlled to inject active and reactive power into the grid. In absence of sunlight, qZSI can be operated as FEC to control reactive power management with the utility grid. To validate the proposed control algorithm, simulation results are presented for grid-connected qZSI powered from solar panel as shown in Fig. 1. Simulation results are formulated into following three sections: (a) Control of qZSI for active and reactive power management, (b) Transient response for qZSI to FEC transition and (c) Control of FEC for reactive power management.Control Algorithm: Control algorithm must satisfy the following requirements: a) When controlled as qZSI, i) Boosting of input voltage must be controlled to achieve the desired output rms voltage ii) Current injected into the grid can be at any power factor - unity, lagging or leading. b) Smooth transition from qZSI to FEC. c) When operated as FEC, i) DC Bus Voltage must be maintained constant and ii) Controlled reactive power management must be achieved. Proposed control algorithm is as shown in Fig. 2. It consists of two types of control blocks. Control blocks which are specific to a type of control algorithm and other which are common for both. Converter reference voltage generation and conventional Sine - Triangle comparison is common to control algorithms of both the inverters. For control of the inverter as qZSI, condition of Vin>Vth must be satisfied which means voltage generated from PV panels is sufficient for grid synchronization. During this mode, S1 and S3 are closed and S2 is opened. qZSI control consists of grid current control and dc bus voltage (Vdc) control. Active and reactive power demand is converted to current proportional and passed through PI controller to generate the converter voltage reference. DC Bus voltage controller gives the shoot-through duty cycle (D). Based on the value of D, shoot-through pulses are ORed with conventional pulses generated by sine-triangle comparison. When Vin>Vth is not satisfied, then the position of relays is changed. S1 and S3 are opened and S2 is closed. Due to this, the solar panel is disconnected from the inverter. The dc bus formed due to series connection of C1 and C2 must be controlled from the grid voltage. The dedicated control block shown in Fig. 2 for FEC generates the active current reference and add it up with required reactive current reference to give the grid current reference. This is passed through PI Controller to give the converter voltage reference. Conventional Sine-triangle comparison is performed to generate switching pulses.SIMULATION RESULTS To verify the control algorithm, the simulation results are shown in Fig. 3. Up to t = 2 sec, the inverter is operated as qZSI injecting controlled active power into the grid. At t = 2 sec, the relays are operated disconnecting the solar panel at the input and now inverter is controlled as FEC. Due to this, the dc bus voltage shoots up which is controlled with the control algorithm. To maintain the dc bus voltage, active current is drawn from the grid. Active current drawn is negligible compared to reactive power managed with the utility grid. Figure 3(a) shows the response of dc bus tracking during the operation. In qZSI mode, active power injection is controlled as shown in Fig. 3(b) and Fig. 3(c). When the inverter is controlled as FEC, reactive power absorbed and supplied are shown in Fig. 3(d) and Fig. 3(e) respectively.qscienc

Full predictive cascaded speed and current control of an induction machine

This paper presents and experimentally validates a new control scheme for electrical drive systems, named cascaded predictive speed and current control (PSCC). This new strategy uses the model predictive control concept. It has a cascaded structure like that found in field-oriented control or direct torque control. Therefore the control strategy has two loops, external and internal, both implemented with model predictive control. The external loop controls the speed, while the inner loop controls the stator currents. The inner control loop is based on Finite Control Set Model Predictive Control (FCS-MPC), and the external loop uses MPC deadbeat, making full use of the inner loop‘s highly dynamic response. Experimental results show that the proposed strategy has a performance that is comparable to the classical control strategies but that it is overshoot-free and provides a better time response

Enhanced Deadbeat Control Approach for Grid-Tied Multilevel Flying Capacitors Inverter

This paper proposes an enhanced Deadbeat Controller (DBC) for a grid-tied Flying Capacitors Inverter (FCI). The proposed DBC guarantees the balancing of the capacitors' voltages while injecting current to the grid with lower Total Harmonics Distortion (THD). The proposed controller has the following advantages: 1) Improved current tracking quality even at zero crossing instants by using a weighted state-space model, 2) Superior steady-state performance (lower current THD) compared to other prediction-based control techniques such as Finite-Control-Set Model Predictive Control, 3) The generated duty cycles are normalized to the common base when the desired state is out of reach within the sampling time, 4) Voltage Ride-Through (VRT) capability, and 5) Robustness to parameters variation. Theoretical analysis, simulation, and experimental results are presented to show the effectiveness of the proposed control technique in ensuring uninterruptible and smooth transfer of energy to the grid during normal/abnormal operating conditions (severe voltage sags, parameters variation, etc.)

Inductive Transfer and Deep Neural Network Learning-Based Cross-Model Method for Short-Term Load Forecasting in Smarts Grids

In a real-world scenario of load forecasting, it is crucial to determine the energy consumption in electrical networks. The energy consumption data exhibit high variability between historical data and newly arriving data streams. To keep the forecasting models updated with the current trends, it is important to fine-tune the models in a timely manner. This article proposes a reliable inductive transfer learning (ITL) method, to use the knowledge from existing deep learning (DL) load forecasting models, to innovatively develop highly accurate ITL models at a large number of other distribution nodes reducing model training time. The outlier-insensitive clustering-based technique is adopted to group similar distribution nodes into clusters. ITL is considered in the setting of homogeneous inductive transfer. To solve overfitting that exists with ITL, a novel weight regularized optimization approach is implemented. The proposed novel cross-model methodology is evaluated on a real-world case study of 1000 distribution nodes of an electrical grid for one-day ahead hourly forecasting. Experimental results demonstrate that overfitting and negative learning in ITL can be avoided by the dissociated weight regularization (DWR) optimizer and that the proposed methodology delivers a reduction in training time by almost 85.6% and has no noticeable accuracy losses.Peer reviewe

A modified PWM three intervals control for a matrix converter in real time

In this paper, the application of the proposed control strategy PWM three intervals with 3×5 matrix converter is presented and analyzed. This control strategy is developed for the control of the multi-phases matrix converter, where the main aim is to ensure the waveform quality of the output voltages and the input currents based on the THD evaluation. Simulation results and real time implementation on dSpace 1103 of 3×5 matrix converter under R-L load are presented for the validation of the proposed control strategy and to clarify the main related advantages

Real-Time Selective Harmonic Mitigation Technique for Power Converters Based on the Exchange Market Algorithm

Hand-in-hand with the smart-grid paradigm development, power converters used in high-power applications are facing important challenges related to efficiency and power quality. To overcome these issues, the pre-programmed Pulse-Width Modulation (PWM) methods have been extensively applied to reduce the harmonic distortion with very low power switching losses for high-power converters. Among the pre-programmed PWM techniques, Selective Harmonic Elimination (SHE) has been the prevailing solution, but recently, Selective Harmonic Mitigation (SHM) stands as a superior alternative to provide further control of the harmonic spectrum with similar losses. However, the large computational burden required by the SHM method to find a solution confines it as an off-line application, where the switching set valid solutions are pre-computed and stored in a memory. In this paper, for the first time, a real-time implementation of SHM using an off-the-shelf mid-range microcontroller is presented and tested. The Exchange Market Algorithm (EMA), initially focused on optimizing financial transactions, is considered and executed to achieve the SHM targets. The performance of the EMA-based SHM is presented showing experimental results considering a reduced number of switching angles applied to a specific three-level converter, but the method can be extrapolated to any other three-level converter topology.Ministerio de Ciencia e Innovación de España TEC2016-78430-RJunta de Andalucía P18-RT-1340Fondo Nacional de Investigación de Qatar NPRP 9-310-2-13