EPE Association: EPE 2018 - DS2g: Renewable Energy Systems II

EPE 2018 - DS2g: Renewable Energy Systems II
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 05: Renewable Energy Power Systems > EPE 2018 - DS2g: Renewable Energy Systems II

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   A Novel Power Conditioning Circuit for Pyroelectric Energy Harvesting
By Alireza KHALIGH [View]
[Download]

Abstract: Pyroelectric effect, a phenomenon that converts temperature variation into electricity, has been recently regarded as a promising solution in thermal energy harvesting due to its high thermal-to-electric efficiency and large power density. However, the current limitation lies in the lack of efficient systems that can both achieve the thermodynamic requirements and convert the harvested energy into useable electricity. Here, a power conditioning circuit specific to pyroelectric conversion cycles has been developed, which generates an 18-25 V triangle bias while extracting energy from an optimized cycle at 1 kHz. The proposed system is comprehensively analyzed, simulated, and validated experimentally on a pseudo pyroelectric material emulator. Both the circuit and a surrogate pyroelectric device are tested at 14 mW pyroelectric power with a harvesting efficiency of 24.3\%.

   Active Damping of LCL-Filter Resonance Using a Digital Resonant-Notch (Biquad) Filter
By Donghua PAN [View]
[Download]

Abstract: The LCL filter is a fundamental component which interfaces a voltage-source inverter (VSI) with a power grid, but on the other hand, it introduces a potential resonance risk which may be harmful to the system stability. In this paper, a digital biquad filter, which consists of a resonance and a notch, is proposed to damp the LCL resonance. By carefully tuning the resonance frequency and the notch frequency of the biquad filter, the LCL resonance is equivalently shifted from an unstable region into a stable one. The proposed method possesses a sensor-less benefit, and it can provide a high control bandwidth as well as a strong robustness. Experimental results acquired from a three-phase grid-connected inverter verify the effectiveness of the biquad filter.

   Binary Search Algorithm-based maximum power point tracking for Photovoltaic system operating under partial shaded conditions
By Hamdan DANIYAL [View]
[Download]

Abstract: This paper presents the study on the application of Binary Search Algorithm (BSA) to determine themaximum power point under partially shaded photovoltaic system. In partially shaded conditions,maximum power point tracking (MPPT) is a challenging task and prone to local maxima problem. TheBSA-based algorithm, together with well-established PSO and another commonly used hill climbingmethod, perturb and observe (P&O) were developed and simulated in MATLAB Simulink. All threealgorithms were examined under 15 different partial shaded test conditions. In order to further analyzethe real time performance of the algorithms, hardware-in-the-loop (HIL) was utilized to emulate thebehavior of the power converter while digital signal processor (DSP) was used to realize the MPPTalgorithms. From the study, the BSA has shown a faster average convergence speed compared to PSO.It is also shown from the study that the BSA was capable to perform MPP tracking under partiallyshaded conditions, with the ability to obtain up to 99 \% tracking efficiency.

   Decoupled Controller for Simultaneous Harmonic and Unbalance Compensation in a multifunctional RES system connected to a LV Distribution Grid
By Huma KHAN [View]
[Download]

Abstract: There is an increasing concern over power quality with more distributed non-linear loads leading tounbalance and voltage harmonics in low-voltage (LV) grid. The traditional way to improve the powerquality in the system is to adopt passive filters or centralized active power filters. Today, many renewable energy-based sources (RESs) are connected to the grid with interfacing converters which can provide harmonic and unbalance compensation. This paper deals with a decoupled controller for simultaneous harmonic and unbalance compensation in a multifunctional smart RES unit. It works on a novel hybrid approach which does not require point-of-common-coupling (PCC) voltage harmonic extraction, multiple phase locked loops (PLLs) or knowledge of distributed load currents. The active power from RES contain both positive and negative sequence current components for improved voltage unbalance compensation. Simulation study for a single RES unit connected to a LV grid with non-linear loads is carried out in PSCAD and results are presented.

   High-Frequency Isolated Three-Phase PV Grid-Tie Converter Based a New Boost Inverter Topology
By Hamdy RADWAN [View]
[Download]

Abstract: This paper proposes a new topology for a three-phase PV grid-tie converter. The Whole system consists of two-stage, high-frequency boost inverter cascaded by rectifier-inverter system. A single-phase high-frequency transformer is used to link both stages and provide galvanic isolation between the AC and DC sides. In the first stage, a new single-stage high-frequency boost inverter is proposed to boost and convert the DC output voltage of the PV array to a high-frequency single-phase square waveform and to realize maximum power point tracking (MPPT). The second stage is rectifier-inverter system that interfaces the first stage to three-phase grid connected. The 5kW three-phase grid connected proposed system has many features such as rising the inverter output voltage level, MPPT, galvanic isolation, small size, high reliability, and light weight. In addition, a grid side controller is used to inject a sinusoidal current into the grid at unity power factor. The proposed topology has been verified analytically by using PSIM software.

   Influence of inverter coupling transformer magnetizing curve on fault ride through operation in grid tied application
By Tomasz CHMIELEWSKI [View]
[Download]

Abstract: This paper presents the topic of grid connected power converter operation during power transformerrecovery inrush current. The phenomenon is as a consequence of temporary voltage dip occurrence.Based on the measurements results and multiple simulations the authors show the relevance of thisphenomenon to the typical Fault Ride-Through (FRT) studies. In this study multiple simulations havebeen run in order to verify the error that can be potentially obtained by not accounting for transformersaturation. This error is expressed by prolonged FRT operation phase due to additional voltage sagoccurring after fault clearing. In the idealized case which was also studied, it has been found that therelevance of power transformer magnetizing curve implementation on the FRT study outcome isclearly visible. However, the model with no saturation in the studied configuration is not critical, dueto the fact that the additional post fault dip magnitude is small and short in duration. Therefore, thetypical FRT algorithm can handle such distortion without exceeding the specified limits. Nonethelessone should keep in mind that the idealized scenario where no saturation is included may vary from theactual output of the real inverter.

   Novel Approach Immune to Partial Shading for Photovoltaic Energy Harvesting from Building Integrated PV (BIPV) Solar Roofs
By Andrii CHUB [View]
[Download]

Abstract: The rapid development of solar photovoltaic (PV) technology facilitates implementation of building integrated PV (BIPV) as a key technology for energy efficient buildings. This study addresses parallel grid integration of microstrings composed of BIPV modules. Existing BIPV products are reviewed. A low number of PV cells per module suggests their series connection to be compatible with microinverters. A concept of a shade tolerant microinverter called Optiverter was applied to BIPV microstrings and compared experimentally to a high-end and a low-end commercial microinverters. Several shading scenarios for three BIPV element types were considered. The Optiverter was compared to several commercial microinverters in terms of maximum power point tracking under unshaded and shaded conditions, power conversion efficiency, maximum power point tracking efficiency, and overall efficiency combining these two parameters.

   Proposal of deterioration evaluation methods of photovoltaic system based on the generation data
By Hitoshi HAYASHIYA [View]
[Download]

Abstract: Evaluation methods of deterioration of a photovoltaic system are proposed and compared based on the on-line generation data at Tokyo Station and Yotsuya Station for about 5 years. The generations of these systems decrease about a few \% per year, which deterioration values are larger than previously reported values. Proposed evaluation methods solve problems of generation fluctuations caused by not only generation efficiency degradation but also weather, temperature, shadow of surrounding buildings and so on. Such on-line evaluation methods of a photovoltaic system have been rarely reported and will be valuable for simple evaluation and monitoring the generation trends of the system.

   Ramp-rate control in large PV plants: Battery vs. Short-Term forecast
By Javier MARCOS [View]
[Download]

Abstract: The changeability in the power produced by utility-scale PV plants caused by shadows due to passingclouds can compromise grid stability. Traditionally, some kind of energy storage systems (ESS) isproposed as the solution to reduce power variations below the limits imposed by new grid codesregulations. However, recent short-term forecast sources open the door to control the variabilitywithout batteries, using only inverter limitation. This option entails some energy curtailment lossesthat has not been yet addressed. This paper quantifies these losses for the first time using a meaningfuldatabase of 5 s one year data for a 38.5 MW PV plant in a perfect forecast scenery. Finally, wecompare the economic cost of installing a lithium-ion battery vs. the inverter limitation solution. Theresults obtained indicate that battery-less strategies must not be neglected for ramp-rate control, sincethey can be more cost-effective using perfect forecast for any ramp value.

   Simultaneous Unbalance and Harmonic Compensation from RESs with Neutral Wire connected to a LV Distribution Grid
By Huma KHAN [View]
[Download]

Abstract: A hybrid power conditioner is proposed for distributed renewable to cater the growing concern of powerquality in a low-voltage (LV) grid. The LV distribution grid is inherently unbalanced and usually feedssingle-phase loads with a neutral return wire. Hence, the system is 4-wire with finite zero sequence orneutral current. A multi-functional renewable energy source (RES) unit based on split-DC link topologyconnected to a 4-wire system is proposed in this paper. It is integrated with a decoupled controller whichcan simultaneously compensate voltage unbalances, neutral current and harmonics of point-of-common-coupling (PCC) voltage. The main advantages of the proposed controller include cancellation of both active and reactive power oscillations during unbalanced current injections, second-order generalised integrator (SOGI) based technique to extract real and imaginary part of zero sequence current, direct harmonic voltage compensation without use of multiple phase locked loops (PLLs) and smooth fault ride-through operation with improved voltage support. Simulation study for a single RES unit connected to a 4-wire LV distribution grid with non-linear loads is carried-out in PSCAD and the results are presented.

   Sizing Local Storage based Li-ion Ultra-capacitors Preventing Sags and Swells of a Voltage in Distribution Networks with PV Plants
By Moshe AVERBUKH [View]
[Download]

Abstract: Local and distributed PV solar plants become more and more widespread power generating facilities providing significant percentage of electricity supply. Together with numerous advantages massive rooftop PV installations (up to 5-10 kW) and utility-scale local plants of 5-20 MW in the low (LV) and middle (MV) voltage distribution networks produce a problem for voltage regulation. Rapid deviations in PV power inherent in this type of energy generate uncertainty in voltage control. Tap changers which are applicable to this purpose have sluggish reaction and occasionally couldn't be able to compensate fast changings of solar electricity. Together with the fluctuations of the consumer's power demands such disturbances can cause dangerous voltage instabilities. As a result, the protection system should disconnect PV stations from electricity supply what negatively affects electricity costs and reliability of the network.One of the possible solutions for mitigation voltage deviations is intermittent energy storage based on ultracapacitors (UC) usage. UC application can improve the voltage stability hence increasing complexity of energy equipment and energy costs. Therefore, the selection of UC bank should be done suitably considering technical and economic aspects of the problem.Current work represents a solution for improving the situation with local voltage regulation based on the appropriate selection of UC bank.

EPE 2018 - DS2g: Renewable Energy Systems II
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 05: Renewable Energy Power Systems > EPE 2018 - DS2g: Renewable Energy Systems II
	[return to parent folder]

	A Novel Power Conditioning Circuit for Pyroelectric Energy Harvesting By Alireza KHALIGH	[View] [Download]
Abstract: Pyroelectric effect, a phenomenon that converts temperature variation into electricity, has been recently regarded as a promising solution in thermal energy harvesting due to its high thermal-to-electric efficiency and large power density. However, the current limitation lies in the lack of efficient systems that can both achieve the thermodynamic requirements and convert the harvested energy into useable electricity. Here, a power conditioning circuit specific to pyroelectric conversion cycles has been developed, which generates an 18-25 V triangle bias while extracting energy from an optimized cycle at 1 kHz. The proposed system is comprehensively analyzed, simulated, and validated experimentally on a pseudo pyroelectric material emulator. Both the circuit and a surrogate pyroelectric device are tested at 14 mW pyroelectric power with a harvesting efficiency of 24.3\%.

	Active Damping of LCL-Filter Resonance Using a Digital Resonant-Notch (Biquad) Filter By Donghua PAN	[View] [Download]
Abstract: The LCL filter is a fundamental component which interfaces a voltage-source inverter (VSI) with a power grid, but on the other hand, it introduces a potential resonance risk which may be harmful to the system stability. In this paper, a digital biquad filter, which consists of a resonance and a notch, is proposed to damp the LCL resonance. By carefully tuning the resonance frequency and the notch frequency of the biquad filter, the LCL resonance is equivalently shifted from an unstable region into a stable one. The proposed method possesses a sensor-less benefit, and it can provide a high control bandwidth as well as a strong robustness. Experimental results acquired from a three-phase grid-connected inverter verify the effectiveness of the biquad filter.

	Binary Search Algorithm-based maximum power point tracking for Photovoltaic system operating under partial shaded conditions By Hamdan DANIYAL	[View] [Download]
Abstract: This paper presents the study on the application of Binary Search Algorithm (BSA) to determine themaximum power point under partially shaded photovoltaic system. In partially shaded conditions,maximum power point tracking (MPPT) is a challenging task and prone to local maxima problem. TheBSA-based algorithm, together with well-established PSO and another commonly used hill climbingmethod, perturb and observe (P&O) were developed and simulated in MATLAB Simulink. All threealgorithms were examined under 15 different partial shaded test conditions. In order to further analyzethe real time performance of the algorithms, hardware-in-the-loop (HIL) was utilized to emulate thebehavior of the power converter while digital signal processor (DSP) was used to realize the MPPTalgorithms. From the study, the BSA has shown a faster average convergence speed compared to PSO.It is also shown from the study that the BSA was capable to perform MPP tracking under partiallyshaded conditions, with the ability to obtain up to 99 \% tracking efficiency.

	Decoupled Controller for Simultaneous Harmonic and Unbalance Compensation in a multifunctional RES system connected to a LV Distribution Grid By Huma KHAN	[View] [Download]
Abstract: There is an increasing concern over power quality with more distributed non-linear loads leading tounbalance and voltage harmonics in low-voltage (LV) grid. The traditional way to improve the powerquality in the system is to adopt passive filters or centralized active power filters. Today, many renewable energy-based sources (RESs) are connected to the grid with interfacing converters which can provide harmonic and unbalance compensation. This paper deals with a decoupled controller for simultaneous harmonic and unbalance compensation in a multifunctional smart RES unit. It works on a novel hybrid approach which does not require point-of-common-coupling (PCC) voltage harmonic extraction, multiple phase locked loops (PLLs) or knowledge of distributed load currents. The active power from RES contain both positive and negative sequence current components for improved voltage unbalance compensation. Simulation study for a single RES unit connected to a LV grid with non-linear loads is carried out in PSCAD and results are presented.

	High-Frequency Isolated Three-Phase PV Grid-Tie Converter Based a New Boost Inverter Topology By Hamdy RADWAN	[View] [Download]
Abstract: This paper proposes a new topology for a three-phase PV grid-tie converter. The Whole system consists of two-stage, high-frequency boost inverter cascaded by rectifier-inverter system. A single-phase high-frequency transformer is used to link both stages and provide galvanic isolation between the AC and DC sides. In the first stage, a new single-stage high-frequency boost inverter is proposed to boost and convert the DC output voltage of the PV array to a high-frequency single-phase square waveform and to realize maximum power point tracking (MPPT). The second stage is rectifier-inverter system that interfaces the first stage to three-phase grid connected. The 5kW three-phase grid connected proposed system has many features such as rising the inverter output voltage level, MPPT, galvanic isolation, small size, high reliability, and light weight. In addition, a grid side controller is used to inject a sinusoidal current into the grid at unity power factor. The proposed topology has been verified analytically by using PSIM software.

	Influence of inverter coupling transformer magnetizing curve on fault ride through operation in grid tied application By Tomasz CHMIELEWSKI	[View] [Download]
Abstract: This paper presents the topic of grid connected power converter operation during power transformerrecovery inrush current. The phenomenon is as a consequence of temporary voltage dip occurrence.Based on the measurements results and multiple simulations the authors show the relevance of thisphenomenon to the typical Fault Ride-Through (FRT) studies. In this study multiple simulations havebeen run in order to verify the error that can be potentially obtained by not accounting for transformersaturation. This error is expressed by prolonged FRT operation phase due to additional voltage sagoccurring after fault clearing. In the idealized case which was also studied, it has been found that therelevance of power transformer magnetizing curve implementation on the FRT study outcome isclearly visible. However, the model with no saturation in the studied configuration is not critical, dueto the fact that the additional post fault dip magnitude is small and short in duration. Therefore, thetypical FRT algorithm can handle such distortion without exceeding the specified limits. Nonethelessone should keep in mind that the idealized scenario where no saturation is included may vary from theactual output of the real inverter.

	Novel Approach Immune to Partial Shading for Photovoltaic Energy Harvesting from Building Integrated PV (BIPV) Solar Roofs By Andrii CHUB	[View] [Download]
Abstract: The rapid development of solar photovoltaic (PV) technology facilitates implementation of building integrated PV (BIPV) as a key technology for energy efficient buildings. This study addresses parallel grid integration of microstrings composed of BIPV modules. Existing BIPV products are reviewed. A low number of PV cells per module suggests their series connection to be compatible with microinverters. A concept of a shade tolerant microinverter called Optiverter was applied to BIPV microstrings and compared experimentally to a high-end and a low-end commercial microinverters. Several shading scenarios for three BIPV element types were considered. The Optiverter was compared to several commercial microinverters in terms of maximum power point tracking under unshaded and shaded conditions, power conversion efficiency, maximum power point tracking efficiency, and overall efficiency combining these two parameters.

	Proposal of deterioration evaluation methods of photovoltaic system based on the generation data By Hitoshi HAYASHIYA	[View] [Download]
Abstract: Evaluation methods of deterioration of a photovoltaic system are proposed and compared based on the on-line generation data at Tokyo Station and Yotsuya Station for about 5 years. The generations of these systems decrease about a few \% per year, which deterioration values are larger than previously reported values. Proposed evaluation methods solve problems of generation fluctuations caused by not only generation efficiency degradation but also weather, temperature, shadow of surrounding buildings and so on. Such on-line evaluation methods of a photovoltaic system have been rarely reported and will be valuable for simple evaluation and monitoring the generation trends of the system.

	Ramp-rate control in large PV plants: Battery vs. Short-Term forecast By Javier MARCOS	[View] [Download]
Abstract: The changeability in the power produced by utility-scale PV plants caused by shadows due to passingclouds can compromise grid stability. Traditionally, some kind of energy storage systems (ESS) isproposed as the solution to reduce power variations below the limits imposed by new grid codesregulations. However, recent short-term forecast sources open the door to control the variabilitywithout batteries, using only inverter limitation. This option entails some energy curtailment lossesthat has not been yet addressed. This paper quantifies these losses for the first time using a meaningfuldatabase of 5 s one year data for a 38.5 MW PV plant in a perfect forecast scenery. Finally, wecompare the economic cost of installing a lithium-ion battery vs. the inverter limitation solution. Theresults obtained indicate that battery-less strategies must not be neglected for ramp-rate control, sincethey can be more cost-effective using perfect forecast for any ramp value.

	Simultaneous Unbalance and Harmonic Compensation from RESs with Neutral Wire connected to a LV Distribution Grid By Huma KHAN	[View] [Download]
Abstract: A hybrid power conditioner is proposed for distributed renewable to cater the growing concern of powerquality in a low-voltage (LV) grid. The LV distribution grid is inherently unbalanced and usually feedssingle-phase loads with a neutral return wire. Hence, the system is 4-wire with finite zero sequence orneutral current. A multi-functional renewable energy source (RES) unit based on split-DC link topologyconnected to a 4-wire system is proposed in this paper. It is integrated with a decoupled controller whichcan simultaneously compensate voltage unbalances, neutral current and harmonics of point-of-common-coupling (PCC) voltage. The main advantages of the proposed controller include cancellation of both active and reactive power oscillations during unbalanced current injections, second-order generalised integrator (SOGI) based technique to extract real and imaginary part of zero sequence current, direct harmonic voltage compensation without use of multiple phase locked loops (PLLs) and smooth fault ride-through operation with improved voltage support. Simulation study for a single RES unit connected to a 4-wire LV distribution grid with non-linear loads is carried-out in PSCAD and the results are presented.

	Sizing Local Storage based Li-ion Ultra-capacitors Preventing Sags and Swells of a Voltage in Distribution Networks with PV Plants By Moshe AVERBUKH	[View] [Download]
Abstract: Local and distributed PV solar plants become more and more widespread power generating facilities providing significant percentage of electricity supply. Together with numerous advantages massive rooftop PV installations (up to 5-10 kW) and utility-scale local plants of 5-20 MW in the low (LV) and middle (MV) voltage distribution networks produce a problem for voltage regulation. Rapid deviations in PV power inherent in this type of energy generate uncertainty in voltage control. Tap changers which are applicable to this purpose have sluggish reaction and occasionally couldn't be able to compensate fast changings of solar electricity. Together with the fluctuations of the consumer's power demands such disturbances can cause dangerous voltage instabilities. As a result, the protection system should disconnect PV stations from electricity supply what negatively affects electricity costs and reliability of the network.One of the possible solutions for mitigation voltage deviations is intermittent energy storage based on ultracapacitors (UC) usage. UC application can improve the voltage stability hence increasing complexity of energy equipment and energy costs. Therefore, the selection of UC bank should be done suitably considering technical and economic aspects of the problem.Current work represents a solution for improving the situation with local voltage regulation based on the appropriate selection of UC bank.