EPE Association: EPE 2014 - DS2g: Renewable Energy and Storage Systems

EPE 2014 - DS2g: Renewable Energy and Storage Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 05: Renewable Energy Power Systems > EPE 2014 - DS2g: Renewable Energy and Storage Systems

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   A Modular/Scalable approach for energy storage and peak shaving applications
By Marcello CHIABERGE, Mirko DE GIUSEPPE, Diego BOERO, Dario GANDINI [View]
[Download]

Abstract: This paper shows a novel design and implementation of a multi purpose power module used to manage energy produced by renewable energy sources and at the same time compensate the discontinuous power absorption from loads, with the final goals to increase power distribution efficiency and grid stability.

   A New Single-stage Three-Phase AC/DC Medium Voltage Step-up Transformer-less Converter with ZVS for Wind Energy Systems
By John LAM, Praveen K. JAIN [View]
[Download]

Abstract: The use of medium voltage DC grid in offshore wind farms power architecture is becoming a promising solution to eliminate the bulky line frequency transformers used in the conventional AC power transmission system. In this power architecture, several wind turbines are first connected to a collective medium voltage DC grid (20~60kV) through an AC/DC power conversion and a medium voltage step-up DC/DC converter. A central step-up DC/DC converter is then used to step-up the medium voltage to high voltage (> 600kV) for HVDC transmission. In order to reduce the number of power conversion stage, this paper proposes a new single-stage three-phase AC/DC medium voltage step-up transformer-less converter for high power wind turbines. The proposed converter is a constant frequency converter and it is controlled by varying the phase-shift between 2 three level circuits. A three-phase boost rectifier is then integrated with the transform-less step-up converter to become a single stage power converter. The converters characteristics and its operating waveforms will be discussed in this paper. Results will be provided to highlight the merits of the proposed converter.

   A Novel Electrolytic Capacitor-less Multi-input DC/DC Converter with Soft-Switching Capability for Hybrid Renewable Energy System
By John LAM, Praveen K. JAIN [View]
[Download]

Abstract: A new multi-input DC/DC converter with soft switching capability and does not require any electrolytic capacitors is proposed in this paper for hybrid renewable energy systems. The proposed converter is applicable to power individual homes that are on or off the grid. There are several features in the proposed converter. First of all, soft-switching capability in the switches is achieved by utilizing an input tapped series inductor and a parallel capacitor across the switch. Secondly, by eliminating the electrolytic capacitors that would be required in the conventional topologies, the reliability of the electronic interface in the renewable energy system is greatly enhanced. The detailed description of the proposed multi-input converter and the circuits operating principles are discussed in this paper. Results are given to highlight the merits of this circuit through a 1.2kW system.

   Adaptive Control of Hybrid Battery Energy Storage Systems under Capacity Fade
By NILANJAN MUKHERJEE, DANI STRICKLAND, Mina VARNOSFADERANI [View]
[Download]

Abstract: There is an increasing call for applications which use a mixture of batteries. These hybrid battery solutions may contain different battery types for example; using second life ex-transportation batteries in grid support applications or a combination of high power, low energy and low power, high energy batteries to meet multiple energy requirements or even the same battery types but under different states of health for example, being able to hot swap out a battery when it has failed in an application without changing all the batteries and ending up with batteries with different performances, capacities and impedances. These types of applications typically use multi-modular converters to allow hot swapping to take place without affecting the overall performance of the system. A key element of the control is how the different battery performance characteristics may be taken into account and the how the power is then shared among the different batteries in line with their performance. This paper proposes a control strategy which allows the power in the batteries to be effectively distributed even under capacity fade conditions using adaptive power sharing strategy. This strategy is then validated against a system of three different battery types connected to a multi-modular converter both with and without capacity fade mechanisms in place.

   Assessing the Accuracy of Loss Estimation Methods for Supercapacitor Energy Storage Devices Operating under Constant Power Cycling
By Ponggorn KULSANGCHAROEN, Christian KLUMPNER, Mohamed RASHED, George Z CHEN, Stuart NORMAN [View]
[Download]

Abstract: This paper assesses different energy loss estimation methods using the supercapacitor model parameters extracted from the electrochemical impedance spectroscopy (EIS). Two energy loss estimation methods are applied to two similar supercapacitors from different manufacturers operating under constant power charge-discharge cycling. The simpler loss method uses only the impedance data that corresponds to the cycle frequency and the instantaneous current data whilst the more complex method uses the detailed impedance vs frequency dependency and the corresponding current harmonics available from the FFT. The experimental loss data (the benchmark) uses integration of instantaneous power processed by the supercapacitor. By comparing the difference between the estimated and the experimental losses, the performance of each method is assessed and the factors that influence the accuracy of the two loss estimation methods as well as their limitations are highlighted.

   FULL SOFT-SWITCHING HIGH STEP-UP DC-DC CONVERTER FOR PHOTOVOLTAIC APPLICATIONS
By Andrei BLINOV, Dmitri VINNIKOV, Volodymyr IVAKHNO, Vladimir ZAMARUEV [View]
[Download]

Abstract: In this paper a full soft-switching high step-up DC-DC converter is introduced as an alternative approach to module integrated converters for photovoltaic applications. The presented operation principle and key equations can be used as design guidelines for component and parameter estimation in practical applications. The proposed DC-DC converter was verified by help of simulations and experiments. Power loss analysis based on the semiconductor datasheet values showed that the converter tends to achieve an efficiency of 92.8\% at the maximum power point.

   Global optimization of hybrid electrical system to decrease fuel consumption or operating cost
By Ivan KRAVTZOFF, Philippe DESSANTE, Jean-Claude VANNIER, Philippe MANFE, Emile MOUNI [View]
[Download]

Abstract: Hybrids systems benefits are strongly dependent on the system design and the control strategy. The strategy choice strongly affect sizing and vice versa. This phenomenon is not always taken into account which leads to a non-optimal sizing of the system. This paper suggests a new method to optimize the design of hybrid power generator system from the point of view of fuel consumption taking into account this interaction. The main idea is to calculate the optimal control strategy of the system energy flux. Then, we can perform, for a given load profile, an optimization of the whole structure to find the best sizing.

   Modeling and Controller design for the Multi-Input PV/Wind Charger
By Cheng-Wei CHEN, Yaow-Ming CHEN [View]
[Download]

Abstract: The objective of this paper is to propose a multi-input converter (MIC) for hybrid PV/wind power charger application which can simplify the power system, reduce the cost and deliver continuous power with higher reliability to the load. The proposed MIC consists of a forward-type pulsating voltage source cell (PVSC) and a buck-boost prime converter can realize the maximum power point tracking (MPPT) function for each PV/wind source. Moreover, due to the isolated configuration, the MIC can adopt PV/wind power sources with larger operation voltage difference. In this paper, the small-signal ac model is derived and the controller design is developed. Computer simulations and experimental results are presented to verify the accuracy of the proposed small signal ac model and the performance of the proposed MIC.

   Novel Isolated Cascaded Half-Bridge Converter for Battery Energy Storage Systems
By Felix JAUCH, Jürgen BIELA [View]
[Download]

Abstract: This paper presents a novel isolated cascaded half-bridge converter for medium voltage battery energy storage systems with three phase legs of series connected modules in star connection. Each module consists of a grid-side half-bridge, a battery-side full-bridge and a medium-frequency transformer providing isolation. The presented modulation ensures grid-side zero-current-switching (ZCS) and batteryside zero-voltage-switching (ZVS). The control system consists of a grid current control as well as a state of-charge (SOC) balancing control for the batteries. Evaluation of the proposed module of a 6.6 kV, 150 kW, 1MWh design example shows an average module efficiency of 97.4 \% including semiconductor and transformer losses. Simulation results verify the converter concept including the applied control structures.

   Seamless Controlled Parallel Bi-directional DC-DC Converter for Energy Storage System
By Takayuki OUCHI, Akihiko KANOUDA, Naoya TAKAHASHI, Minoru MOTEKI [View]
[Download]

Abstract: A scalable parallel bidirectional DC-DC converter system, which enables efficient seamless controlusing an H-bridge topology, was developed and evaluated. Although the unified control structure issimple, four drive-mode, both charge and discharge with buck/boost, can be handled. The proposedsystem was extended for use in simple parallel converter management. This scheme achieves highefficiency over a wide load range, especially for light loads. The only hardware required is a powerline and communication cable connection. All other functions are provided by software and operateautonomously. A 5-kW prototype converter was constructed and evaluated, and a four-unit parallelconverter system was tested and confirmed to work well, changing load between 20-kW discharge and20-kW charge.

   Sensitivity Analysis for the Design of an Energy Management Scheme of Supercapacitor Buffering in a Regulated DC Bus
By Matti LIUKKONEN, Seppo OVASKA, Jorma KYYRÄ [View]
[Download]

Abstract: This paper constitutes a solid connection between theory and practice for electrical quantities for thedesign of supercapacitor buffering in regulated DC-bus systems. Transparently validated theory is proposedto be used for decision making that bases on estimates of sensitivity indices, expanded uncertaintyintervals, and the Monte-Carlo method. This approach can be used for engineering of various DCpowerdistribution systems that are increasingly applied in hybrid powertrains of electric vehicles andDC microgrids. Results conclude a clear connection between theory and practice, and a well establishedapproach with examples of its usage can be easily adopted.

   Stabilization of Back-to-Back Converter in Wind Generation System Connected to the Grid: IDA-PBC versus PI Control
By Seleme Isaac SELEME-JR, Leonardo T. F. SOARES, Selênio R. SILVA [View]
[Download]

Abstract: Wind energy generation systems connected to the grid have become an important research subject concerning stability and energy optimization. This article addresses the control of a Back-to-Back converter connecting a Permanent Magnet Synchronous Generator to the grid. The system uses an Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC). Comparison of classical PI approach with the proposed approach is made. Experimental results are provided.

   Towards a new technological solution for Community Energy Storage
By Diogo VARAJÃO, Luis M. MIRANDA, RUI E. ARAÚJO [View]
[Download]

Abstract: Energy storage in low voltage grid is receiving increased attention due to renewables integration and consumption growth, challenges faced nowadays by grid operators. In this work, a study of main implementation issues for community energy storage (CES) is presented along with a comparison between possible solutions for the bidirectional isolated power conversion system (PCS) to interface a battery pack with the electric power grid. The aim of this research is to increase the power density of the power converter and keeping simultaneously the same reliability of traditional solutions. These goals are pursued to be achieved through the reduction of the conversion stages and utilization of new optimization methodologies to reduce the volume of the passive components. The proposed topology for the PCS is based on a matrix converter (MC) that performs a direct AC to AC conversion between the grid and a high-frequency transformer (HFT). With this solution it is possible to eliminate the traditional DC-link capacitor and obtain a single-stage power conversion with bidirectional power flow capability. This proposed solution is evaluated and compared with a conventional two-stage topology through extensive simulation. Two prototypes systems were designed for a 10kW PCS to connect the three-phase 230/400Vrms, 50Hz mains to a battery pack with voltage range of 320V to 490V. Simulation results are presented to assess the power quality provided by the front-end and the battery side converters, as well as performance evaluation and efficiency analysis.

EPE 2014 - DS2g: Renewable Energy and Storage Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 05: Renewable Energy Power Systems > EPE 2014 - DS2g: Renewable Energy and Storage Systems
	[return to parent folder]

	A Modular/Scalable approach for energy storage and peak shaving applications By Marcello CHIABERGE, Mirko DE GIUSEPPE, Diego BOERO, Dario GANDINI	[View] [Download]
Abstract: This paper shows a novel design and implementation of a multi purpose power module used to manage energy produced by renewable energy sources and at the same time compensate the discontinuous power absorption from loads, with the final goals to increase power distribution efficiency and grid stability.

	A New Single-stage Three-Phase AC/DC Medium Voltage Step-up Transformer-less Converter with ZVS for Wind Energy Systems By John LAM, Praveen K. JAIN	[View] [Download]
Abstract: The use of medium voltage DC grid in offshore wind farms power architecture is becoming a promising solution to eliminate the bulky line frequency transformers used in the conventional AC power transmission system. In this power architecture, several wind turbines are first connected to a collective medium voltage DC grid (20~60kV) through an AC/DC power conversion and a medium voltage step-up DC/DC converter. A central step-up DC/DC converter is then used to step-up the medium voltage to high voltage (> 600kV) for HVDC transmission. In order to reduce the number of power conversion stage, this paper proposes a new single-stage three-phase AC/DC medium voltage step-up transformer-less converter for high power wind turbines. The proposed converter is a constant frequency converter and it is controlled by varying the phase-shift between 2 three level circuits. A three-phase boost rectifier is then integrated with the transform-less step-up converter to become a single stage power converter. The converters characteristics and its operating waveforms will be discussed in this paper. Results will be provided to highlight the merits of the proposed converter.

	A Novel Electrolytic Capacitor-less Multi-input DC/DC Converter with Soft-Switching Capability for Hybrid Renewable Energy System By John LAM, Praveen K. JAIN	[View] [Download]
Abstract: A new multi-input DC/DC converter with soft switching capability and does not require any electrolytic capacitors is proposed in this paper for hybrid renewable energy systems. The proposed converter is applicable to power individual homes that are on or off the grid. There are several features in the proposed converter. First of all, soft-switching capability in the switches is achieved by utilizing an input tapped series inductor and a parallel capacitor across the switch. Secondly, by eliminating the electrolytic capacitors that would be required in the conventional topologies, the reliability of the electronic interface in the renewable energy system is greatly enhanced. The detailed description of the proposed multi-input converter and the circuits operating principles are discussed in this paper. Results are given to highlight the merits of this circuit through a 1.2kW system.

	Adaptive Control of Hybrid Battery Energy Storage Systems under Capacity Fade By NILANJAN MUKHERJEE, DANI STRICKLAND, Mina VARNOSFADERANI	[View] [Download]
Abstract: There is an increasing call for applications which use a mixture of batteries. These hybrid battery solutions may contain different battery types for example; using second life ex-transportation batteries in grid support applications or a combination of high power, low energy and low power, high energy batteries to meet multiple energy requirements or even the same battery types but under different states of health for example, being able to hot swap out a battery when it has failed in an application without changing all the batteries and ending up with batteries with different performances, capacities and impedances. These types of applications typically use multi-modular converters to allow hot swapping to take place without affecting the overall performance of the system. A key element of the control is how the different battery performance characteristics may be taken into account and the how the power is then shared among the different batteries in line with their performance. This paper proposes a control strategy which allows the power in the batteries to be effectively distributed even under capacity fade conditions using adaptive power sharing strategy. This strategy is then validated against a system of three different battery types connected to a multi-modular converter both with and without capacity fade mechanisms in place.

	Assessing the Accuracy of Loss Estimation Methods for Supercapacitor Energy Storage Devices Operating under Constant Power Cycling By Ponggorn KULSANGCHAROEN, Christian KLUMPNER, Mohamed RASHED, George Z CHEN, Stuart NORMAN	[View] [Download]
Abstract: This paper assesses different energy loss estimation methods using the supercapacitor model parameters extracted from the electrochemical impedance spectroscopy (EIS). Two energy loss estimation methods are applied to two similar supercapacitors from different manufacturers operating under constant power charge-discharge cycling. The simpler loss method uses only the impedance data that corresponds to the cycle frequency and the instantaneous current data whilst the more complex method uses the detailed impedance vs frequency dependency and the corresponding current harmonics available from the FFT. The experimental loss data (the benchmark) uses integration of instantaneous power processed by the supercapacitor. By comparing the difference between the estimated and the experimental losses, the performance of each method is assessed and the factors that influence the accuracy of the two loss estimation methods as well as their limitations are highlighted.

	FULL SOFT-SWITCHING HIGH STEP-UP DC-DC CONVERTER FOR PHOTOVOLTAIC APPLICATIONS By Andrei BLINOV, Dmitri VINNIKOV, Volodymyr IVAKHNO, Vladimir ZAMARUEV	[View] [Download]
Abstract: In this paper a full soft-switching high step-up DC-DC converter is introduced as an alternative approach to module integrated converters for photovoltaic applications. The presented operation principle and key equations can be used as design guidelines for component and parameter estimation in practical applications. The proposed DC-DC converter was verified by help of simulations and experiments. Power loss analysis based on the semiconductor datasheet values showed that the converter tends to achieve an efficiency of 92.8\% at the maximum power point.

	Global optimization of hybrid electrical system to decrease fuel consumption or operating cost By Ivan KRAVTZOFF, Philippe DESSANTE, Jean-Claude VANNIER, Philippe MANFE, Emile MOUNI	[View] [Download]
Abstract: Hybrids systems benefits are strongly dependent on the system design and the control strategy. The strategy choice strongly affect sizing and vice versa. This phenomenon is not always taken into account which leads to a non-optimal sizing of the system. This paper suggests a new method to optimize the design of hybrid power generator system from the point of view of fuel consumption taking into account this interaction. The main idea is to calculate the optimal control strategy of the system energy flux. Then, we can perform, for a given load profile, an optimization of the whole structure to find the best sizing.

	Modeling and Controller design for the Multi-Input PV/Wind Charger By Cheng-Wei CHEN, Yaow-Ming CHEN	[View] [Download]
Abstract: The objective of this paper is to propose a multi-input converter (MIC) for hybrid PV/wind power charger application which can simplify the power system, reduce the cost and deliver continuous power with higher reliability to the load. The proposed MIC consists of a forward-type pulsating voltage source cell (PVSC) and a buck-boost prime converter can realize the maximum power point tracking (MPPT) function for each PV/wind source. Moreover, due to the isolated configuration, the MIC can adopt PV/wind power sources with larger operation voltage difference. In this paper, the small-signal ac model is derived and the controller design is developed. Computer simulations and experimental results are presented to verify the accuracy of the proposed small signal ac model and the performance of the proposed MIC.

	Novel Isolated Cascaded Half-Bridge Converter for Battery Energy Storage Systems By Felix JAUCH, Jürgen BIELA	[View] [Download]
Abstract: This paper presents a novel isolated cascaded half-bridge converter for medium voltage battery energy storage systems with three phase legs of series connected modules in star connection. Each module consists of a grid-side half-bridge, a battery-side full-bridge and a medium-frequency transformer providing isolation. The presented modulation ensures grid-side zero-current-switching (ZCS) and batteryside zero-voltage-switching (ZVS). The control system consists of a grid current control as well as a state of-charge (SOC) balancing control for the batteries. Evaluation of the proposed module of a 6.6 kV, 150 kW, 1MWh design example shows an average module efficiency of 97.4 \% including semiconductor and transformer losses. Simulation results verify the converter concept including the applied control structures.

	Seamless Controlled Parallel Bi-directional DC-DC Converter for Energy Storage System By Takayuki OUCHI, Akihiko KANOUDA, Naoya TAKAHASHI, Minoru MOTEKI	[View] [Download]
Abstract: A scalable parallel bidirectional DC-DC converter system, which enables efficient seamless controlusing an H-bridge topology, was developed and evaluated. Although the unified control structure issimple, four drive-mode, both charge and discharge with buck/boost, can be handled. The proposedsystem was extended for use in simple parallel converter management. This scheme achieves highefficiency over a wide load range, especially for light loads. The only hardware required is a powerline and communication cable connection. All other functions are provided by software and operateautonomously. A 5-kW prototype converter was constructed and evaluated, and a four-unit parallelconverter system was tested and confirmed to work well, changing load between 20-kW discharge and20-kW charge.

	Sensitivity Analysis for the Design of an Energy Management Scheme of Supercapacitor Buffering in a Regulated DC Bus By Matti LIUKKONEN, Seppo OVASKA, Jorma KYYRÄ	[View] [Download]
Abstract: This paper constitutes a solid connection between theory and practice for electrical quantities for thedesign of supercapacitor buffering in regulated DC-bus systems. Transparently validated theory is proposedto be used for decision making that bases on estimates of sensitivity indices, expanded uncertaintyintervals, and the Monte-Carlo method. This approach can be used for engineering of various DCpowerdistribution systems that are increasingly applied in hybrid powertrains of electric vehicles andDC microgrids. Results conclude a clear connection between theory and practice, and a well establishedapproach with examples of its usage can be easily adopted.

	Stabilization of Back-to-Back Converter in Wind Generation System Connected to the Grid: IDA-PBC versus PI Control By Seleme Isaac SELEME-JR, Leonardo T. F. SOARES, Selênio R. SILVA	[View] [Download]
Abstract: Wind energy generation systems connected to the grid have become an important research subject concerning stability and energy optimization. This article addresses the control of a Back-to-Back converter connecting a Permanent Magnet Synchronous Generator to the grid. The system uses an Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC). Comparison of classical PI approach with the proposed approach is made. Experimental results are provided.

	Towards a new technological solution for Community Energy Storage By Diogo VARAJÃO, Luis M. MIRANDA, RUI E. ARAÚJO	[View] [Download]
Abstract: Energy storage in low voltage grid is receiving increased attention due to renewables integration and consumption growth, challenges faced nowadays by grid operators. In this work, a study of main implementation issues for community energy storage (CES) is presented along with a comparison between possible solutions for the bidirectional isolated power conversion system (PCS) to interface a battery pack with the electric power grid. The aim of this research is to increase the power density of the power converter and keeping simultaneously the same reliability of traditional solutions. These goals are pursued to be achieved through the reduction of the conversion stages and utilization of new optimization methodologies to reduce the volume of the passive components. The proposed topology for the PCS is based on a matrix converter (MC) that performs a direct AC to AC conversion between the grid and a high-frequency transformer (HFT). With this solution it is possible to eliminate the traditional DC-link capacitor and obtain a single-stage power conversion with bidirectional power flow capability. This proposed solution is evaluated and compared with a conventional two-stage topology through extensive simulation. Two prototypes systems were designed for a 10kW PCS to connect the three-phase 230/400Vrms, 50Hz mains to a battery pack with voltage range of 320V to 490V. Simulation results are presented to assess the power quality provided by the front-end and the battery side converters, as well as performance evaluation and efficiency analysis.