Power Conditioning System Research Articles

Theoretical and experimental investigation of R&W and W&R SMES coils wound with large-scale MgB2 Rutherford cables operated around liquid hydrogen temperature

We have developed the system called Advanced Superconducting Power Conditioning System (ASPCS) composed of a Superconducting Magnetic Energy Storage (SMES), a fuel cell and a water electrolyzer for effective use of renewable energy such as wind and solar power generation. We have been investigating about the SMES coil using the large-scale Rutherford-type conductors made of commercially-available MgB2 wires. Due to strain sensitivity even before heat treatment for MgB2 production, the design for large-scale Rutherford cables both in the wind and react (W&R) method, and the react and wind (R&W) method applied to coil fabrication has to be done cautiously to prevent the degradation of the IC by the optimizing design parameters such as the twist pitch and the cable compaction. Especially for the R&W method using heat-treated wires, other factors like handling during the coil production process which affect the conductor and coil IC should be also considered. To evaluate the applied strains during the manufacturing process, we conducted theoretical investigation on the strains applied to individual filaments caused by wire-bending. We developed a test coil designed for the R&W method based on analyzing those factors. Furthermore, we measured the coil IC-B-T characteristics and compared to those of other test coils made by the W&R method.

LCL filter design and robust converter side current feedback control for grid-connected Proton Exchange Membrane Fuel Cell system

Proton Exchange Membrane Fuel Cell (PEMFC) systems are environment-friendly systems that can be used as distributed power generation (DPG) system. As DPG units are usually utilized in weak power distribution systems, the grid inductance variations should be investigated during the control design stage of the grid-tied fuel cell systems. In recent years, LCL filter is broadly utilized to grid connection of DPG units, and the proper design of this filter is an important issue. In this paper, converter side current feedback (CSCF) method has been applied due to its innate damping feature to integrate PEMFC fuel cell system through LCL filter into weak power distribution system. The impact of delay should be considered as it limits the stability region of the resonance frequency of the CSCF control method especially, in the presence of wide variations of the grid inductance. Precise-tuned LCL filter design and consequently, the proper choice of the resonance frequency can remarkably affect the performance of the CSCF control. An adequate-tuned design procedure for LCL filter parameters has been proposed in this paper. Step-by-step tuning of the PR controller parameters has also been included to enhance the power quality. The grid-tied fuel cell system with modified-Y-Source inverter and LCL filter as an interface between inverter and grid has been simulated to analyze the quality of the injected power. Simulation results in MATLAB/Simulink environment verify the suitable performance of the proposed power conditioning system as well as its stable operation versus wide variation of weak grid inductance.

Temporary Fault Ride-Through Method in Power Distribution Systems with Distributed Generations Based on PCS

The current practice of Distributed Generation (DG) disconnection for every fault in distribution systems has an adverse effect on utility and stable power trading when the penetration level of DGs is high. That is, in the process of fault detecting and Circuit Breaker (CB) reclosing when a temporary fault occurs, DGs should be disconnected from the Point of Common Coupling (PCC) before CB reclosing. Then all DGs should wait at least 5 minutes after restoration for reconnection and cannot supply the pre-bid power in power market during that period. To solve this problem, this paper proposes a control method that can keep operating without disconnection of DG. This control method is verified through modeling and simulation by the PSCAD/EMTDC software package for distribution systems with DGs based on PCS (Power Conditioning Systems) and CB reclosing protection.

An improved power conditioning system for grid integration of solar power using ANFIS based FOPID controller

Power loss become common while integrating with common grid and in specific when power produced through Solar. This is the very lacking area which this proposal implements an Adaptive Neuro Fuzzy Inference System (ANFIS) based controller of Fractional Order Proportional Integral Derivative (FOPID) used for Tracking of Maximum PP of Grid Integrated Solar Power Conditioning System. The proposed work advances with different ambient light conditions for maximum power point traction. In this work a clear-cut Photo Voltaic (PV Cell) model has been developed and an intensive and operative training data have been extracted from the developed controller. This produced dataset have been the feeder input for the ANFIS structure in turn to locate the Tracking of Maximum PP (MPPT). Traction of MPPT is done, the FOPID controller is enforced by matching the voltage from the array of Photo Voltaic cell with attained or reference voltage produced by the ANFIS structure. In the meantime driving this PV array, DC to DC converter's duty cycle is controlled for producing maximum power from the structure. The duty cycle in FOPID controller is generated through calculating the error within the reference voltage and PV voltage. Those values are then simulated through Math Lab and the Simulation results show that this proposed work efficiency is better than the regularly employed controllers in the solar power production and conditioning system

A Hybrid PV-Battery System for ON-Grid and OFF-Grid Applications—Controller-In-Loop Simulation Validation

In remote locations such as villages, islands and hilly areas, there is a possibility of frequent power failures, voltage drops or power fluctuations due to grid-side faults. Grid-connected renewable energy systems or micro-grid systems are preferable for such remote locations to meet the local critical load requirements during grid-side failures. In renewable energy systems, solar photovoltaic (PV) power systems are accessible and hybrid PV-battery systems or energy storage systems (ESS) are more capable of providing uninterruptible power to the local critical loads during grid-side faults. This energy storage system also improves the system dynamics during power fluctuations. In present work, a PV-battery hybrid system with DC-side coupling is considered, and a power balancing control (PBC) is proposed to transfer the power to grid/load and the battery. In this system, a solar power conditioning system (PCS) acts as an interface across PV source, battery and the load/central grid. With the proposed PBC technique, the system can operate in following operational modes: (a) PCS can be able to work in grid-connected mode during regular operation; (b) PCS can be able to charge the batteries and (c) PCS can be able to operate in standalone mode during grid side faults and deliver power to the local loads. The proposed controls are explained, and the system response during transient and steady-state conditions is described. With the help of controller-in-loop simulation results, the proposed power balancing controls are validated, for both off-grid and on-grid conditions.

Optimal current calculation for a PMSG based wind energy system integrated into an unbalanced weak grid

Grid connection is an important consideration when it comes to integrating an energy source. A common problem with the existing wind energy conversion systems is that they are often located far from energy consumption centres. Owing to their remote location these systems are sometimes forced to connect with weak distribution networks which are usually designed for small linear loads. When the nature of these loads is changed, the voltage level at the point of common coupling may go above or below the nominal value which may result in power system instability. To improve the voltage variation, this study discusses an optimal current calculation technique based on Thevenin equivalent parameters of an electrical network. The functional capability of the technique is demonstrated with the help of a traditional converter topology utilised as a power conditioning system for a permanent magnet synchronous generator connected to a weak grid. The system in particular monitors a medium voltage distribution line, measures line load impedance and redistributes the currents in a way that provides maximised power transfer into a network with least incurred losses. A real-time controller with built-in data acquisition/field-programmable gate array modules is used for the execution of experimental investigations.

An Experimental Strategy for Characterizing Inductive Elesctromagnetic Energy Harvesters.

Condition monitoring of high voltage power lines through self-powered sensor systems has become a priority for utilities with the aim of detecting potential problems, enhancing reliability of the power transmission and distribution networks and mitigating the adverse impact of faults. Energy harvesting from the magnetic field generated by the alternating current flowing through high voltage lines can supply the monitoring systems with the required power to operate without relying on hard-wiring or battery-based approaches. However, developing an energy harvester, which scavenges the power from such a limited source of energy, requires detailed design considerations, which may not result in a technically and economically optimal solution. This paper presents an innovative simulation-based strategy to characterize an inductive electromagnetic energy harvester and the power conditioning system. Performance requirements in terms of the harvested power and output voltage range, or level of magnetic core saturation can be imposed. Different harvester configurations, which satisfy the requirements, have been produced by the simulation models. The accuracy and efficiency of this approach is verified with an experimental setup based on an energy harvester, which consists of a Si-steel magnetic core and a power conditioning unit. For the worst-case scenario with a primary current of 5 A, the maximum power extracted by the harvester can be as close as 165 mW, resulting in a power density of 2.79 mW/cm3.

Selecting an Effective ESS Installation Location From the Perspective of Reactive Power

When an entire power system blacks out, the system operator uses a self-starting generator to initiate the recovery procedure that starts the priority generator using a transmission line. Because most self-starting generators are pumped storage generators, they are located at a distance from the priority generators. This results in long transmission lines that can cause overvoltage during the recovery process through the line charging effect. Herein, the above issue is resolved by replacing the self-starting generator with an energy storage system (ESS) to reduce the possibility of overvoltage generation. The transmission line is shortened by moving the ESS closer to the priority generator, thus utilizing its flexible installation feature: an ESS has no location constraints for installation. In addition, this study determines an effective location for the ESS to minimize the reactive power requirements: moving the ESS closer to the priority generator reduces the required reactive power. Thus, the capacity of the power conditioning system can be reduced, which is advantageous in terms of cost-effectiveness.

Multi‐input high step‐up inverter with soft‐switching capability, applicable in photovoltaic systems

In this study, a new multi-input high step-up inverter, based on isolated soft-switching DC-DC converter blocks is proposed. Each of these blocks can provide zero-voltage and zero-current switching for its semiconductors, which improve power efficiency. The interesting feature of this DC-DC converter is using bidirectional switches to generate both positive and negative output voltage levels in each DC-DC block with an appropriate control scheme. Each DC-DC converter operates by simple pulse width modulation control through fixed frequency and has two degrees of freedom, which provide the capability of output voltage regulation or maximum power point tracking. The proposed inverter consists of the cascaded connection of these DC-DC converters at their output terminal. This inverter can operate with high voltage gain, where the output voltage of each DC-DC converter is regulated. Furthermore, it can generate more output voltage levels with less number of DC-DC blocks. All these advantages make the proposed inverter suitable for photovoltaic power conditioning systems. In this study, the theoretical analysis with steady-state waveforms, design constraints, resonant tank analysis and comparison study are given. Then, experimental results of both the proposed inverter and its DC-DC blocks are presented.

Battery-less Power Conditioning System using Mechanical Fly WheelBattery-less Power Conditioning System using Mechanical Fly Wheel

Considering the abundant sunlight so as the insolation available over many months in the Indian sub-continent, renewable energy can be easily harvested using solar photovoltaic array to supplement the grid power. This work proposes such an arrangement through a battery less UPS system. The need for battery less UPS system arises since batteries used in the conventional UPS system have less life time and a major concern of environmental pollution. Considering a premises/ organization where there is a power back up facility like a diesel generator, the role of batteries in the UPS system is limited and used for only few seconds between the mains power failure and the turning on of generator. Hence for such short term power requirements, a Kinetic Energy based medium for storage such as fly-wheel based energy storage can be effectively utilized instead of the electrochemical batteries. Hence the combination of solar PV based power generation along with a battery less online power conditioning system to supply a critical load is the proposed in this scheme.

Design and construction of a digital solar array simulator with fast dynamics and high performance

This paper presents the hardware implementation of a digital solar array simulator (DSAS) to evaluate and validate the operation of maximum power point tracking (MPPT) algorithms and photovoltaic (PV) inverters used in solar power conditioning systems (SPCSs). The required criteria for designing and setting up a genuine SAS are high-accuracy static behavior, fast transient response, and high flexibility for the emulation of the different PV modules. A four-phase interleaved buck converter is chosen as the proposed power stage of the SAS because of its advantages of power management, filtering reduction requirements, and output ripple minimization. The proposed SAS control system has been digitally implemented by a digital signal processor (DSP)-based controller, in which third-order integral-lead compensator and resistive feedback method have been chosen to reproduce precise and stable operating points. Experimental results confirm the proper and satisfactory steady-state operation and dynamic response of the proposed DSAS.

A System Engineering Approach Using FMEA and Bayesian Network for Risk Analysis—A Case Study

This paper uses a system engineering approach based on the Failure Mode and Effect Analysis (FMEA) methodology to do risk analysis of the power conditioner of a Proton Exchange Membrane Fuel Cell (PEMFC). Critical components with high risk, common cause failures and effects are identified for the power conditioner system as one of the crucial parts of the PEMFCs used for backup power applications in the telecommunication industry. The results of this paper indicate that the highest risk corresponds to three failure modes including high leakage current due to the substrate interface of the metal oxide semiconductor field effect transistor (MOSFET), current and electrolytic evaporation of capacitor, and thereby short circuit, loss of gate control, and increased leakage current due to gate oxide of the MOSFET. The MOSFETs, capacitors, chokes, and transformers are critical components of the power stage, which should be carefully considered in the development of the design production and implementation stage. Finally, Bayesian networks (BNs) are used to identify the most critical failure causes in the MOSFET and capacitor as they are classified from the FMEA as key items based on their Risk Priority Numbers (RPNs). As a result of BNs analyses, high temperature and overvoltage are distinguished as the most crucial failure causes. Consequently, it is recommended for designers to pay more attention to the design of MOSFETs’ failure due to high leakage current owing to substrate interface, which is caused by high temperature. The results are emphasizing design improvement in the material in order to be more resistant from high temperature.

RETRACTED: Design and implementation of novel soft switching method based DC-DC converter with non-isolated coupled inductor in solar system using FPGA

Abstract DC-DC converter is a basic element for stand-alone photovoltaic power conditioning system. Here, a new topology called an ANFIS (Adaptive Neuro-Fuzzy Inference System) controller based soft switched DC/DC converter with non-isolated coupled inductor has been simulated and presented for improving the power of stand-alone PV system. Both AC analysis and voltage gain is calculated for the proposed converter along with the presence of gain analysis. The steady state/dynamic performance of the non-isolated coupled inductor based converter have been analyzed using MATLAB simulation. The topology has been developed to reduce the input current ripple and to enhance the operating power conversion efficiency. To improve the dynamic response of the converter, Proportional, Integral and Derivative (PID) controller is implemented. However, the linear controllers are influenced by the system parameters of the converters; it results in reduced voltage regulation for wide variations in system parameters. Hence to over rid the limitations of analog controllers and to improve the closed-loop performance of the proposed converter, a simple ANFIS controller is proposed. Consequently, its performance of the proposed controller is compared and analyzed with PID and FL (Fuzzy Logic) controller. It is seen that the implementation of the proposed controller improves the efficiency of the system and also reduces the voltage drop across the switching operation to enhance the operating power conversion efficiency. From the analysis, it is concluded that the proposed converter improves the voltage regulation of the proposed converter. Steady state error, peak time, peak overshoot and THD are used to evaluate the performance of the proposed system. A 200 W, 100 kHz prototype model is developed and demonstrated. Finally, Experimental results are carried out to validate the efficiency of this method using FPGA – Spartan6. From the observed results, it can be revealed that the suggested converter is a feasible alternative to PV applications.

Fault Ride-Through Characteristics of Small Wind Turbines

There is significant potential for an increase in the use of kilowatt-class small wind turbines (SWTs) in Japan due to reduced limitations with respect to installation, despite their high cost. At this stage, the Japanese grid code has not been considered sufficiently with respect to grid-connected SWTs, and the addition of fault ride-through (FRT) requirements for SWTs has been requested. Moreover, the FRT of SWTs is challenging to achieve owing to the low inertia constants when compared with those of large-scale wind turbines, which result in significant acceleration of the rotor speed and an increase in the input voltage of the power conditioning system (PCS) during FRT operation. In this study, FRT field tests were conducted on SWT systems against a voltage dip with a duration of ~1 s, and it was confirmed that the SWT systems satisfied the FRT requirements for photovoltaic (PV) systems connected to low-voltage distribution lines in Japan. The behaviors of the rotational speed of the SWTs and the PCS input voltage in an FRT operation were then analyzed, and it was noted that the increase in the PCS input voltage with the overspeed of the turbine can reach the upper limit and make the PCS cease operation, which indicates failure of the FRT. The overvoltage, therefore, requires restriction using a method such as pitch control, furling, and electrical and/or mechanical brakes.

Development of a high-energy-density portable/mobile hydrogen energy storage system incorporating an electrolyzer, a metal hydride and a fuel cell

A hydrogen energy storage system for portable/mobile applications such as personal power sources and unmanned underwater vehicles is developed. An application-oriented design and system integration strategy are newly suggested to maximize energy density while incorporating conventional technologies for the electrolyzer (Ely), the metal hydride (MH), and the polymer electrolyte membrane fuel cell (PEMFC). To improve both the energy density and usability, the systems for charging and discharging are separated. The charging component is composed of a water Ely (0.5 Nm3 h−1) and an MH cooling device as one system. The discharging component consists of an MH (900 NL H2), a PEMFC stack (50 W), and a power conditioning system (PCS) as a single system. The MH material and engineering properties are investigated to find an MH that is suitable for the target system. The hybrid design and operating strategy of the PEMFC and PCS are developed to maximize energy density. The prototype system provides a nominal power output of 31.5 W at 12 V for 38 h with one recharging. We find it significant that the discharging component shows an energy density of 410 Wh L−1, which is twice that of conventional energy storage systems at the 2.9-L level.

Exploration of interactive thermal influence characteristics of power and air conditioning system based on 1D/3D coupling calculation in electric vehicle underhood

The thermal problems in the underhood are serious in the integrated thermal management of electric vehicles. The interaction of the heat dissipation components in the underhood affects the heat exchange and working performance, which affects its driving range and safety. This paper takes the interactive thermal influence into consideration between the battery, motor and air conditioning system, builds an underhood thermal management system framework of electric vehicles, and establishes a 1D/3D coupling model for the integrated systems. Only the components in the underhood are studied in 3D. The impact of load change of the air conditioning system and power system on heat transfer performance of another system is studied under different heat exchanger layouts. The results show that the cooling effect of the power system decreases with the load of the air conditioning system increasing when the condenser is placed in front of the radiators. When the condenser is behind the radiators, the air conditioning system load change has no significant effect on the heat dissipation effect of the power system. For both arrangements, the load change of the power system has an evident influence on the refrigeration process of the air conditioning system. The dissipated heat of the condenser decreases as the power system load increases, and the COP increases gradually. At the same time, the cooling performance number is introduced to evaluate the heat dissipation capacity of the power system and the air conditioning system. The smaller the cooling performance number, the stronger the heat dissipation capability of the system, and vice versa, the worse the heat dissipation capability. So it can further optimize the cooling characteristics and safety of the entire electric vehicle by comprehensively considering the arrangement or the targeted optimization of the heat exchangers to improve the integrated thermal management system of EVs.

Single-Phase 13-Level Power Conditioning System for Peak Power Reduction of a High-Speed Railway Substation

The control and operation of a single-phase 13-level power conditioning system (PCS) for peak power reduction of a high-speed railway substation (HSRS) are proposed. This PCS is a single-phase 3100 V, 2 MVA 13-level H-bridge multi-level inverter structure. It has excellent power quality. It is easy to serialize by voltage. In addition, the DC bus power of each cell inverter is supplied by lithium-ion batteries. The generalized reduction gradient optimization algorithm based on past load pattern is applied to the power management system for peak power reduction of HSRS. The phase detector and power controller for the control of a single-phase PCS based on virtually coordinated axes using an all-pass filter are expected to be robust to external disturbances with fast response characteristics. This study also proposes an adapted select switch (ASS) method that can change the switching depending on the operation state of PCS and the state of charge (SOC) of the battery to minimize battery imbalance by controlling each cell inverter of the H-bridge. The validity of the proposed system was confirmed by PSiM simulation and experiments using a demonstration system of 6 MW PCS and 2.68 MWh batteries at one of Gyeongbu high-speed line substations in Korea.

Comprehensive influences measurement and analysis of power converter low frequency current ripple on PEM fuel cell

To deeply understand the influences of power converter's low frequency current ripple (LFCR) and harmonics on a proton exchange membrane fuel cell (PEMFC) in its power conditioning system (PCS), a comprehensive measurement and analysis of the influences of LFCR and harmonics on PEMFC's performance and durability is investigated in this paper. Based on an equivalent circuit model of PEMFC stack and a mechanism model for evaluating the LFCR effects on the PEMFC, this paper studies primarily and systematically the comprehensive influences of LFCR and harmonics on PEMFC performances and durability, such as (1) degrading the PEMFC performance, (2) shortening the lifetime of PEMFC, (3) reducing the stack output power, (4) lowing its availability efficiency, (5) producing more heat and raising the PEMFC temperature, (6) consuming more fuel, and (7) decreasing the fuel utilization. Finally, a Horizon 300 W PEMFC stack is implemented and tested.

Real-Time Detection of Interharmonics and Harmonics of AC Electric Arc Furnaces on GPU Framework

In this paper, a method based on the multiple synchronous reference frame analysis is recommended and implemented to detect time-varying harmonics and interharmonics of rapidly fluctuating asymmetrical industrial loads. The experimental work has been carried out on a typical three-phase alternating current arc furnace installation. In the recommended method, the reference frame is rotated in both directions at speeds corresponding to the positive and negative sequences of all harmonics and all interharmonics 5 Hz apart. To extract the direct current components of the transformed d–q quantities, a low-pass filter is employed. In order to keep the delay of the filter at zero frequency less than a few ms, Kalman estimation technique has been used. Back transformation is then applied for each harmonic and interharmonic component to obtain their positive- and negative-sequences of the associated harmonic and interharmonic in the actual line current waveforms. Parallel computing technique has been applied for the real-time detection of both the phase and the amplitude of all harmonics and interharmonics. This is achieved on NVDIA Jetson TX1 graphics processing unit framework for a sample industrial plant. The developed system is shown to be useful for fast and accurate generation of reference signals for the controllers of the advanced technology power conditioning systems which successfully compensates interharmonics, harmonics, and flicker of the rapidly fluctuating nonlinear industrial loads.

Single-phase transformerless power conditioner based on a two-leg of a nine-switch converter

An interesting solution for problems associated with system voltage, such as sags and swells, as well as those associated with current such as low power factor and harmonic distortion is the unified power quality conditioner. However, one of its drawbacks is the high number of semiconductor devices since its conventional topology presents two full-bridge converters in a back-to-back configuration. Although the six-switch two-leg converter has a feature of presenting two sets of single-phase output terminals, the same as two full-bridge converters, but with a reduced number of switches (six, instead of eight), it has never been used in single-phase power conditioning systems. Therefore, the aim of this paper is to propose a single-phase transformerless power conditioner based on the six-switch two-leg converter. In this solution, there are two sets of single-phase outputs, each set behaving as an independent converter. The top unit of the converter is connected in parallel to the load by means of a series LC filter tuned to a specific frequency, working as a hybrid power filter and being responsible for the dc-link voltage regulation and the compensation of current harmonics generated by the non-linear load. The bottom unit works as a dynamic voltage restorer and it is responsible for compensating harmonics, sags or swells in the grid voltage, in such way that the load receives a sinusoidal voltage waveform. The challenges of the single-phase transformerless power conditioner that is proposed in this paper are different of the three-phase systems based on nine-switch converter previously proposed in literature. Dealing with the circulating current makes mathematical model and the modulation strategy completely different and, therefore, all equations have been developed for this specific single-phase power conditioner application. The proposed power conditioner presents four main advantages when compared with other configurations available in literature: (a) it is a transformerless solution; (b) it has a reduced number of switches; (c) it has a reduced dc-link voltage and rated power because of its hybrid power filter characteristics; (d) it does not have to handle with dc-link voltage unbalance. Experimental results demonstrate the validity and the effectiveness of the proposed topology.