Power Electronics for Photovoltaic Power Systems

Vilathgamuwa, D.M.; Nayanasiri, Dulika; Gamini, Shantha

doi:10.2200/s00638ed1v01y201504pel008

Cited by 27 publications

(18 citation statements)

References 41 publications

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“…Generally, the voltage of the ESS (battery and/or supercapacitor) is lower than the dc-link voltage and the polarity of the energy storage, and its output is set to the same with respect to the common ground. The dc-dc bidirectional converter is suited well for this type of application, because proper control of the switches regulate the dc-link power fluctuations by directing them to the energy storage [33][34][35]. This is a simple converter, which can be used in high-power applications where the switch rating of the converter becomes the key concern [23,36].…”

Section: Dc-dc Converter Controllermentioning

confidence: 99%

“…The states of the S1 and S2 switches directly affect the charging and discharging of the inductor. As shown in Figure 4, the HB dc-dc bidirectional converter operates in the buck mode only when the ESS is charging and operates in the boost mode only when it discharging [33]. The space state equations for the buck converter, as in Figure 4b, and for the boost converter, as in Figure 4c, in continuous current mode operation are discussed below, assuming that all the circuit elements are ideal.…”

Section: Space State Model Of Bidirectional Dc-dc Convertermentioning

confidence: 99%

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Grid Integration and Power Smoothing of an Oscillating Water Column Wave Energy Converter

et al. 2018

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This paper applies model predictive control (MPC) for the power processing of an oscillating water column (OWC) wave energy conversion (WEC) system to achieve smooth power delivery to the grid. The particular air turbine design adopted in this study produces large power pulses ranging from 0 to 1 MW in magnitude, and thus, direct connection to the grid is practically impossible, especially in weak grid conditions. Therefore, energy storage is an essential element that should be integrated into this particular WEC system in order to absorb power pulses and thereby ensure smooth delivery of power to the grid. Taking into account the repetitive nature, duration, and magnitude of the power pulses, this study has chosen "supercapacitor" as the suitable energy storage technology. The supercapacitor energy storage (SCES) is integrated into the dc-link of the back-to-back power converter of the WEC system through a bidirectional dc-dc converter. In order to achieve the desired operation of this complex power converter arrangement, a finite control set MPC strategy is proposed in this paper. Performance of the proposed energy storage system (ESS) and control strategy are evaluated through computer simulations. Simulation results show that the proposed SCES system and the control strategy are able to achieve smooth power delivery to the grid amidst power pulses coming from the generator. exhale and inhale air streams through the open end of the chamber. Energy of the air stream is then converted into electricity with the aid of a turbine coupled generator. The commonly used turbines are bidirectional which extract energy from both the inhale and exhale streams.The Australian maritime college, in collaboration with the Wave Swell Energy Ltd., has developed a new OWC air turbine technology, which has been recognized as an efficient and simple design compared with many other OWC technologies [6,7]. This particular configuration has passive, non-return air flow valves built into its chamber, which activate during the exhale stage and equalize the pressure inside the chamber to the atmosphere, which allows the rising water column to reach its maximum height. This creates a higher differential pressure during the inhale stage resulting in high velocity air stream through the turbine. Since this particular air turbine extracts energy only during the inhale stage, the output power inherently becomes discrete pulses. These large and discrete power pulses create major operational issues, such as frequency deviations, voltage sags/swells, and instabilities if delivered to the grid without smoothing. Therefore, energy storage is an essential feature that should be incorporated into the power converter of the WEC system. Nevertheless, in contrast to wind energy or tidal energy turbines, where the rotational speed should be changed according to the wind speed or tidal flow speed, the unidirectional air-turbine used in this study does not necessarily require variable speed operation. Therefore, according to [8], the turbine speed can be ...

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Section: Dc-dc Converter Controllermentioning

confidence: 99%

Section: Space State Model Of Bidirectional Dc-dc Convertermentioning

confidence: 99%

Grid Integration and Power Smoothing of an Oscillating Water Column Wave Energy Converter

et al. 2018

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“…The advantages of using a battery as a source of energy storage in power systems is well known. In addition to the reserve energy capacity that it provides, there is considerable literature recommending the use of a BESS to effectively deal with frequency transients, especially in standalone power systems such as terrestrial microgrids, major power grids and in shipboard power systems [8][9][10][11]. The BESS integrated with the power system has to be fast in its response to changes in the power system and also have sufficient capacity to bring the state of the power system back to normal operating conditions.…”

Section: Introductionmentioning

confidence: 99%

“…In the system shown in Figure 1, the BESS is directly connected to the DC-link of the frequency converter as opposed to the majority of literature, which uses a DC-DC converter to interface the battery to the DC-link [9,10,12]. The absence of this interfacing converter reduces the complexity of the energy storage system while at the same time retaining control of the battery current.…”

Section: Introductionmentioning

confidence: 99%

Frequency Transient Suppression in Hybrid Electric Ship Power Systems: A Model Predictive Control Strategy for Converter Control with Energy Storage

2018

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This paper aims to understand how the common phenomenon of fluctuations in propulsion and service load demand contribute to frequency transients in hybrid electric ship power systems. These fluctuations arise mainly due to changes in sea conditions resulting in significant variations in the propulsion load demand of ships. This leads to poor power quality for the power system that can potentially cause hazardous conditions such as blackout on board the ship. Effects of these fluctuations are analysed using a hybrid electric ship power system model and a proposed Model Predictive Control (MPC) strategy to prevent propagation of transients from the propellers into the shipboard power system. A battery energy storage system, which is directly connected to the DC-link of the frequency converter, is used as the smoothing element. Case studies that involve propulsion and service load changes have been carried out to investigate the efficacy of the proposed solution. Simulation results show that the proposed solution with energy storage and MPC is able to contain frequency transients in the shipboard power system within the permissible levels stipulated by the relevant power quality standards. These findings will help ship builders and operators to consider using battery energy storage systems controlled by advanced control techniques such as MPC to improve the power quality on board ships.

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“…In fact, the application of battery energy storage in WEC systems is also not new [14]. The common approach of integrating an ESS, in the form of a battery bank and/or a supercapacitor bank, is the use of an interfacing dc-dc or dc-ac converter [11,15,16]. This enables direct control over the charge/discharge current of the ESS.…”

Section: Introductionmentioning

confidence: 99%

A Model Predictive Control-Based Power Converter System for Oscillating Water Column Wave Energy Converters

et al. 2017

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Abstract:Despite the predictability and availability at large scale, wave energy conversion (WEC) has still not become a mainstream renewable energy technology. One of the main reasons is the large variations in the extracted power which could lead to instabilities in the power grid. In addition, maintaining the speed of the turbine within optimal range under changing wave conditions is another control challenge, especially in oscillating water column (OWC) type WEC systems. As a solution to the first issue, this paper proposes the direct connection of a battery bank into the dc-link of the back-to-back power converter system, thereby smoothening the power delivered to the grid. For the second issue, model predictive controllers (MPCs) are developed for the rectifier and the inverter of the back-to-back converter system aiming to maintain the turbine speed within its optimum range. In addition, MPC controllers are designed to control the battery current as well, in both charging and discharging conditions. Operations of the proposed battery direct integration scheme and control solutions are verified through computer simulations. Simulation results show that the proposed integrated energy storage and control solutions are capable of delivering smooth power to the grid while maintaining the turbine speed within its optimum range under varying wave conditions. Keywords: active front end rectifier; finite control set-model predictive control (FCS-MPC); two-level voltage source inverter; wave energy conversion (WEC)

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Power Electronics for Photovoltaic Power Systems

Cited by 27 publications

References 41 publications

Grid Integration and Power Smoothing of an Oscillating Water Column Wave Energy Converter

Grid Integration and Power Smoothing of an Oscillating Water Column Wave Energy Converter

Frequency Transient Suppression in Hybrid Electric Ship Power Systems: A Model Predictive Control Strategy for Converter Control with Energy Storage

A Model Predictive Control-Based Power Converter System for Oscillating Water Column Wave Energy Converters

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