Showing papers presented at "International Power Electronics and Motion Control Conference in 2018"

Development of a Simple Fuzzy Logic Controller for DC-DC Converter

Abstract: Control of DC-DC converters is a complex task due to the inherent nonlinearity. There is intensive research in developing newer control strategies which should ensures stability of output voltage under varying load, input voltage and parameters variations. The paper is aimed to present possibilities of use fuzzy logic controller to control output voltage of a phase-shifted PWM (PS-PWM) soft-switching DC-DC converter. The converter is a full bridge DC-DC converter with a controlled output rectifier and an active snubber on the secondary side. Despite proven advantages of use of a fuzzy logic control for DC-DC converters, one of the main drawback can be considered computational demand, which could negatively affects the response of a converter on sudden changes of load and raise up the price of the converter, due that there is needed a microcontroller with higher computational capacity. To suppress the high computational demand of a FLC controller there is presented a look-up table controller, which is derived from the original FLC controller. In the paper are described two different suitable interpolation methods for look up table controller composition, and assessment of advantages and disadvantages of both methods.

Field Bus for Data Exchange and Control of Modular Power Electronic Systems with High Synchronisation Accuracy

Abstract: In this paper, a new field bus protocol based on the IEEE 802.3 Ethernet standard is proposed. It enables fast data exchange between and synchronised control in the modules of modular power electronic systems. With increasing switching frequency, a highly accurate synchronisation of the different modules is a necessary requirement for a control bus. The proposed field bus protocol provides a stable and efficient scheme including a novel data frame structure and allows a synchronisation accuracy of ±4 ns on the 1 GBit Ethernet standard.For validation of the new protocol a prototype system has been built and measurement results are provided. Eventually, the implementation has been found to meet the specification during testing.

Modelling and Design of a Medium Frequency Transformer for High Power DC-DC Converters

Abstract: Dual Active Bridge (DAB) converters are an interesting solution for battery interfaces in storage systems for traction applications. Due to the environmental conditions and space limitations, the design of the transformer and cooling system is crucial for achieving a high power density. Therefore in this paper a detailed design of a transformer with integrated liquid cooling structure and high isolation voltage is presented. Analytical models for the design are presented and verified with FEM simulations and measurements on a prototype system.

Design Considerations of GaN Transistor Based Capacitive Wireless Power Transfer System

Abstract: The paper discusses and evaluates design of capacitive wireless power transfer (WPT) system. The capacitive WPT can replace a conventional inductive WPT for example in applications where metallic objects are placed close to receiver or transceiver. Main limitation for wider application of the capacitive WPT is due to small coupling capacitance between two surfaces in limited space. Therefore, to utilize capacitive WPT system the switching frequency should be as high as possible. Challenges associated with design of capacitive WPT system operating in MHz range are discussed in this paper. In the paper it is described WPT system that consists of two copper plates to transfer power from the primary side to the secondary side. Some calculation considerations of resonant network is given in the paper. The high switching of inverter transistors requires high performance transistors with optimized driver circuit. The design of GaN transistor based inverter and driver circuit is discussed and experimental results are shown.

Output Power Regulation of a Virtual Oscillator Controlled Inverter

Abstract: An output power regulation strategy is presented for a virtual oscillator controlled inverter. With multiple inverters feeding a microgrid, an output power regulation technique is imperative to utilize these distributed energy sources efficiently and reducing the distribution line stress and losses, and equitably sharing revenue streams. It is demonstrated that a PI controller can be used to regulate the output power by tuning the current feedback gain of the virtual oscillator controller. Adjusting the current feedback gain affects the inverter terminal voltage magnitude. In order to investigate the local stability of the system, a linearization and eigenvalues analysis is performed. Further, explicit conditions are specified to ensure the local stability of the system with varying controller and load parameters. A polynomial Lyapunov function is determined using the sum of squares technique to investigate the global stability of the system. A brief overview illustrating the effect of variations in VOC-parameters on the system performance is provided. Simulation results establish the merits of the proposed control scheme.

Design of a Power Flow Control Converter for Bipolar Meshed LVDC Distribution Grids

Abstract: Flexible power flow control is one of the main challenges in the development of the meshed low voltage direct current distribution system. The most widely adopted approach to achieve flexible power control in the network is to use various solid-state based solutions which are rated for the peak power of the grid. In this paper, we propose a solution based on a converter which has several times smaller power rating than the grid power rating. Due to the multi-port nature of the proposed solution, it is well suited for the bipolar networks.

A Multifunctional Integrated Onboard Battery Charger for Plug-in Electric Vehicles (PEVs)

Abstract: This paper proposes a CuK converter based integrated battery charger for plug-in electric vehicles (PEVs), Proposed bidirectional DC/DC converter is capable of performing buck/boost function during all modes of vehicle operation. It operates as a power factor correction (PFC) converter during plug-in charging mode, and as conventional single stage inverting buck/boost converter in driving and regenerative braking modes. Selection of a wide range of battery voltages and adequate control over braking can be achieved with the proposed multi-functional converter. In addition, size, weight and cost of the charger are also reduced, as it involves minimum number of components compared to existing buck/boost converters used in chargers. The proposed converter is highly suitable for onboard charger of PEVs. Simulation are performed on MATLAB/Simulink environment and a laboratory prototype of the aforementioned converter has been built to validate its feasibility.

Hybrid Microgrid System Design with Renewable Energy Sources

Abstract: This study presents both a hybrid microgrid system design with renewable energy and their control methods, analysis result. This renewable energy resources (RES) consist of 33kW PVs, 100kW fuel cell stack and a 50kW wind turbine with permanent magnet synchronous generator (PMSG). PV plant includes the PV arrays and DC-DC boost converter. Fuel cell plant includes the fuel cell stacks and DC-DC boost converter. The wind energy plant contains the wind turbine, PMSG, uncontrolled rectifier and DC-DC boost converter. The boost converter connected to PV plant has been controlled by using incremental conductance maximum power point tracking algorithm (IC-MPPT A). Both the boost converters of the wind energy system and fuel cell system have been operated with PI controllers. The switching element of all boost converters is M OSFE T. The switching frequency for boost converters of the wind energy system and fuel cell system is 30 kHz and 50 kHz for boost converter connected PV array. The hybrid microgrid has been coupled on 1000V DC-bus bar. 400V/120 kV transformer and 120 kV, 50 Hz AC supply have been used to create the grid model. To convert from DC to AC, as the topology, full bridge inverter circuit has been used and IGBT has selected as the switching element. Phase locked loop (PLL) algorithm has been used as a control for the AC voltage generated at the inverter output to be the same phase, frequency and amplitude with the grid. The system has been operated under the various operating conditions such as wind speed and solar irradiation. And despite these variables, the desired results have been obtained from the system.

Feedforward Finite Control Set Model Predictive Position Control of PMSM

Abstract: This paper presents a predictive controller that simultaneously controls the position, speed and the current of PMSM. The controller is based on finite control set model predictive control approach. Motion profile generator is used for the generation of reference signals. Signals generated there enter into the controller and act as feedforward signals that are evaluated inside of a cost function with other predictions. Measured position is used as a feedback and the speed and load torque are estimated by Kalman filter. The control is formulated in the dq coordinate frame. Simulation results show that the performance of the proposed position controller is significantly improved by using the proposed feedforward terms in the cost function when comparing to the cost function without these terms. The controller with improved cost function was also experimentally verified with Texas Instruments DSP.

Comparison of a Two-Phase Interleaved Boost Converter and Flyback Converter

Abstract: A big majority of electricity energy is generated from naturel sources such as coal, petroleum etc. in all over the world. The reserve of this sources are decreasing. However, the demand of electricity is increasing day by day. The researchers head for alternative energy sources such as biomass, geothermal, marine energies, hydropower, wind and solar. The most important of these is the solar energy. The studies about solar energy are increased in recent years. This study deals with the design and analysis of different converter topologies which are two phase interleaved boost converter and flyback converter in terms of structure, efficiency. Each system is consists of a photovoltaic (PV) module, converter topology and Maximum Power Point Tracking (MPPT) algorithm. The MPPT algorithm is necessary to acquire maximum power from the PV module. The power capacity of each system is 295 W and the input voltage of converters are around 54 V. While the output voltage of two-phase interleaved boost converter is 232 V, the output voltage of flyback converter is 238 V. In this study, it is determined that the efficiency of flyback converter is better than the two-phase interleaved boost converter.

Design and Simulation of Bistable Piezoceramic Cantilever for Energy Harvesting from Slow Swinging Movement

Abstract: This paper deals with a kinetic energy harvesting device which could harvest electricity from slow swinging movements. This device is based on a bistable design of a piezoelectric cantilever with a tip mass. An additional nonlinear magnetic stiffness is created by magnetic systems for an operation between two stable positions. A slow movement in gravity field could change a potential function of this device and the first stable position is becoming unstable position and this resonator is starting to free oscillate in the second stable position or vice versa. Piezoelectric layers could provide electricity during free oscillating operation in both stable positions. This system could be fixed on a robotic arms, industrial platforms or human body which change a system position in gravity field. For example, a human hand is moved during walking with a slow swing movement and this movement could be used for energy harvesting. This energy harvesting device could generate useful electricity for wearable electronics or biomedical implants. This paper provides mechatronic models which could predict output power during walking.

Transient and Steady-State Analysis of a SEPIC Converter by an Average State-Space Modelling

Abstract: This study presents a simple and effective methodology for analyzing transient and steady state behavior of a Single Ended Primary Inductance Converter (SEPIC), operating in a continuous current mode (CCM). The proposed technique uses an average state-space modelling approach including power losses in converter elements. This approach makes possible obtaining analytical solutions for the converter currents and voltages and allows examining different characteristics of converter behavior, e.g. efficiency, output to input voltage ratio, input current, transient times, and elements stresses. This methodology is valuable for keeping the converter design in compliance with design requirements, including dynamics, and reduces the need for accurate time domain simulations. This approach can be useful for analyzing other types of high order converters.

DC-DC Buck Converter Parameter Identification Based on a White-Box Approach

Abstract: This paper proposes to use a white-box approach to identify the parameters of an electronic DC-DC buck converter. It discretizes the differential equations governing the dynamic of such system, which are used to identify the parameters of the electronic components of the converter and the control loop. The proposed method is used to calculate the system parameters from the open loop and closed loop outputs, that is, the steady state and transient state stages of the output signals. The approach is validated by comparing simulation results from PSIM models of the converter with experimental data obtained from a commercial non-synchronous buck converter. Both simulation and experimental results show the feasibility and accuracy of the proposed approach in identifying the parameters of the converter, thus being feasible to obtain a full representation of such power converter.

Sensorless Control of Wind Turbine Conversion Equipped with a DFIG Using MPPT Strategy

Abstract: Wind energy is an inexhaustible clean energy source. However, its cost is still too high to compete with traditional fossil sources. The yield of a conversion system depends on different parameters: the power of the wind, the conversion system curve and the generator ability for responding the fluctuations in the wind. In this paper, a sensorless controller based on Doubly-Fed Induction Generator (DFIG) mathematical model and vector control using MPPT strategy is presented. The proposed control can directly ensure the position speed via simple mathematical equation by measuring the stator voltage, the rotor and stator currents. The principle of speed estimation is described and simulated by using Matlab/Simulink software. The simulation results demonstrate the feasibility of the control strategy based on the measurement of the output power and it is offered to maximize the power delivered to network despite all the parameter changes via MPPT strategy.

Structural Parameter Optimization to Reduce Cogging Torque of the Consequent Pole In-Wheel Motor

Abstract: The structural parameter optimization to reduce cogging torque of the consequent pole in-wheel motor (CPM) is studied in this paper. The analysis model of calculating the cogging torque is derived by the energy equations and finite-element analysis (FEA) is carried out for accurate numerical simulation of the cogging torque. The difference between the consequent pole structure and the conventional structure is investigated firstly. Then the influences of structural parameters on the cogging torque, such as pole arc coefficient and widths of slot opening are calculated and analyzed. Beyond that, the slot-pole match and curved iron core to reduce cogging torque are studied. Through the analysis of calculation results, the optimized structural parameters are obtained, and experiment results from two prototypes demonstrate the correctness and feasibility of the proposed methods.

Modeling and Analysis of EMI and Overvoltage Phenomenon in SiC Inverter Driven Motor at High Switching Frequency

Abstract: This paper explains the advantages of using Wide Bandgap (WBG) semiconductor made of Silicon Carbide (SiC) by the characterization of power efficiency and losses of SiC inverter of 15kVA/540V and the analysis of EMI and overshoot of commutation at high switching frequency. The measured power efficiency of inverter can be higher 99%. This inverter also implemented in to electromechanical chain to drive an aeronautic motor (type PMSM). However, faster switching (higher di/dt and dv/dt) of SiC inverter, at higher frequencies, it is necessary to identify the electromagnetic impact (EMI) and the overshoot switching voltage. The experimental results will be shown the interesting of this technology and the impact at high switching frequency.

A New Technique to Identify Induction Machine Rotor Parameters During Dynamic Operation and Low Speed

Abstract: Resulting control performance of induction machine drives relies on accurate rotor flux linkage estimation. Deviation of temperature dependent rotor parameter leads to detuning of the machine model and thus needs to be compensated online. By exploiting and separating the machine's saturation saliency information, it is possible to set up a tuning method to accurately identify machine model rotor parameter and thus to identify temperature even at low speed and dynamic operation. The method proposed is divided into an initial commissioning phase and a temperature identification phase during machine operation. Within this study a mathematical description of the temperature influence on rotor flux estimation is given. Moreover, detailed performance verification of the method is shown using a 100kW induction machine for traction applications.

Accurate Rotor Position Detection for Low-Speed Operation of Switched Reluctance Drives

Abstract: Switched reluctance machines (SRMs) exhibit the advantages of low-cost production and high reliability. Position sensorless control can contribute significantly to further improve these properties. Due to the salient structure of the SRM, the stator inductance can be used to determine the rotor position $\theta_{\mathrm{e}}$ from injected current peaks at standstill and low speeds. Exact torque and force control of SRMs requires highly accurate information about the machine's rotor position. Therefore, the purpose of this paper is to expose the advantages of position estimation algorithms implemented on field-programmable gate array (FPGA). The algorithm includes an inductance identification procedure and sophisticated signal filtering. Besides improvement measures based on modeling and signal conditioning, a method for reduction of the injection currents is demonstrated and evaluated. The developed algorithm considers the mutual coupling effect and is verified by simulation and experiment.

Impact of the Different Parasitic Inductances on the Switching Behavior of SiC MOSFETs

Abstract: This paper experimentally investigates into the effects of parasitic inductances on the switching performance of a SiC MOSFET half bridge. As the switching dynamics of wide-bandgap power semiconductors are by magnitudes larger compared to silicon devices, the parasitic elements in the switching cell become increasingly important, as they limit the current and voltage slopes and cause oscillations. A thorough understanding of those effects is necessary for the design of highly efficient and integrated next-generation power electronic converters. An implementation method to realize cheap and well-reproducible variable inductors in the nanohenry range is presented. Furthermore, a test PCB equipped with SiC MOS-FETs is built and double pulse experiments are carried out under the variation of all relevant inductances in the switching cell. The results are analyzed with respect to the switching performance and differences between the switching transients of Si and SiC devices are demonstrated and explained with respect to the parasitic elements.

Introduction to the Analysis of Harmonics and Resonances in Large Offshore Wind Power Plants

Abstract: The concern for power quality has been on the rise in recent years for all kinds of electric power systems. Harmonic analysis is especially interesting in the case of Offshore Wind Power Plants (OWPPs) due to the special susceptibility of these systems to harmonic issues and to the inherent differences in their behavior with respect to other electric networks. The aim of this article is to provide an overview of the basic concepts for harmonic analysis in OWPPs and to outline the typical assessment procedure used to this day. Some of the limitations of current industry practice will be outlined, as well as some possible complementary approaches for its improvement.

Analysis and Verification on CLLC Resonant Bidirectional DC-DC Converter Based on Variable Frequency Phase Difference Control Principle

Abstract: A Dual Active Bridge (DAB) converter controlled by phase difference or phase-shift control has several disadvantages such as soft-switching limitation and increase of reactive power under the condition of unbalanced two-port dc voltages. As an effective solution to those technical issues, Variable Frequency Phase Difference Control (VF-PDC) for a symmetrical series Resonant tank (CLLC)-applied Bidirectional DC-DC converter (RBDC) is newly developed, and its performances on soft-switching and reactive power reduction are analyzed theoretically and demonstrated by a experiment of the prototype.

Comparison of Inverter Topologies Suited for Integrated Modular Motor Drive Applications

Abstract: In this paper, various inverter topologies are compared for integrated modular motor drive (IMMD) applications. Two-level voltage source inverter (2L-VSI), three-level voltage source inverter (3L-VSI) and series/parallel combinations of these topologies with system level modularity are compared in terms of voltage and current harmonic spectrum, passive component sizes and motor drive efficiency. New generation wide band-gap GaN power semiconductor devices are utilized in modular topologies and they are compared with a conventional IGBT motor drive. The effect of phase-shifting between the PWM carrier signals of parallel connected modules and its contribution to size reduction is investigated. IMMD structure has proven to have a superior efficiency compared to conventional motor drives, thanks to the utilization of GaNs. It has been shown that over 98% motor drive efficiency can be achieved for 8kW IMMD by using a newly proposed topology where 2L-VSI converters are connected both in series and parallel on the DC link.

PV Source Inverter with Voltage Compensation for Weak Grid Based on UPQC Configuration

Abstract: In this paper, the distributed generation (DG) inverter design based on unified power quality conditioner (UPQC) configuration is presented to solve the power quality problems for sensitive load under weak grid condition. The integrated DG consists of a series connection inverter and a shunt connection inverter. The series connection inverter acts as a dynamic voltage restorer (DVR) to mitigate voltage problem due to cable impedance in submarine cable and fluctuated load. The shunt connection inverter works as a back-up power source like PV system with Maximum Power Point Tracing (MPPT) when the voltage problem is seriously lower or higher than the operation standard. Battery system, as a back-up source when low irradiance condition, will be considered in this paper too. This paper describes a simple method for controlling the series connection inverter while the shunt connection operates as a back-up for sensitive load. Finally, the proposed method for integrated PV source is verified through the PSiM simulation.

V/f with stabilizing loops versus FOC of Spoke-PM rotor SM drive: control with experiments

Abstract: In this paper, two sensorless control strategies for the spoke-PM rotor synchronous motor drive in a wide speed range are studied: the V/F control with two stabilizing loops and the sensorless field-oriented control (FOC). The FOC was implemented for comparison, only. To improve drive dynamics and responses during transients, the standard V/f control has been enhanced with two stabilizing loops, which provide corrections for both voltage vector amplitude and voltage vector position angle. The main advantages of the V/f control with stabilizing loops are the simplicity, low computation time and lower calibration effort, which makes it desirable for home appliances such pumps and refrigerator compressors. The novelty consists of a new and more simpler formulae for the voltage vector amplitude correction than the ones already existent. The motion sensorless control of the spoke-PM rotor synchronous motor drive is obtained via model-based stator flux estimation using the “active flux” concept. Experimental results between 200 rpm and 2000 rpm validate the two control systems. Finally, a comparison between the experimental results employing both control systems has been done.

Modeling and Analysis of a New Voltage Regulation Method for Surface-Mounted Permanent Magnet Synchronous Generator

Abstract: The current trend for future aircraft is the adoption of the More Electric Aircraft (MEA) concept. The electrical based starter-generator (S/G) system is one of the core ideas from the MEA concept. Usually, the starter-generator produces constant torque as a starter and constant power as a generator. Surface-mounted permanent magnet synchronous generator (SPMSG) is suitable for a high speed operation, which can improve the power density of electrical system. But it is difficult for SPMSG to keep producing constant power for a wide speed operation. This paper proposes a new voltage regulation method of SPMSG for a wide-speed-range operation. After analyzing the stability of two types of single current regulator (SCR), the $\pmb{q}$ -axis SCR is applied to enhance the field weakening ability of SPMSG, which means that the speed operation range of SPMSG is extended. The proposed voltage regulation method has been implemented in simulation over a speed range of 10,000∼24,000rpm. The results indicate that the system with this proposed method can respond quickly and remain stable, and the dynamic performance improved significantly in sudden change of the load.

The Design and Analysis of a Two-Stage PV Converter with Quasi-Z Source Inverter

Abstract: The single-phase photovoltaic (PV) systems are being widely researched due to several environmental and financial advantages. The PV converters are implemented either in single stage of two-stage topologies according to intermediate dc bus requirements. In the two-stage topologies, the recent researches are based on transformerless structures to eliminate bulky and lossy transformer isolation. Therefore, several methods including stray current grounding have been proposed in the literature to obtain isolation without the use of transformer. This paper proposes a two-stage PV converter with quasi Z-source (qZS) inverter in the second stage. The first stage of PV converter is comprised by a conventional boost converter that the maximum power point tracking (MPPT) controller is improved with integral regulator addition to incremental conductance algorithm. The MPPT efficiency of improved system is measured as 98.8% regarding to the designed controller. In addition to its efficiency, MPPT controller stabilized the intermediate dc bus voltage against the various irradiation values applied to PV plant. The qZS network is designed to ensure continuous conduction mode (CCM) operation considering shoot-through and non-shoot-through states. The switching control of H-bridge inverter is realized by the designed grid tracking controller that samples grid voltage as a reference input and decomposes to detect phase, frequency, and amplitude values. The power factor of inverter output is measured at 0.988 and total harmonic distortion (THD) ratios of current and voltage waveforms are at 1.71 %.

DC-DC Boost Converter Stability with Constant Power Load

Abstract: In this paper, the fuzzy logic control (FLC) is presented to address the instability effects of constant power load, and how to regulate the output voltage of a DC-DC Boost converter. The constant power load has negative incremental resistance, which makes the system unstable under a small disturbance on the load. To evaluate the performance, the proposed method is simulated by a MATLAB-SIMULINK model. Furthermore, the proposed concept is validated experimentally using a field programmable gate Array FPGA-Based Hardware-in-the-Loop Simulation by hardware description language.

Comparative Analysis of Small-Signal Dynamics in Virtual Synchronous Machines and Frequency-Derivative-Based Inertia Emulation

Abstract: This paper presents a comparison of small-signal dynamics for a current controlled Virtual Synchronous Machine (VSM), a voltage controlled VSM and a df/dt-based control strategy for inertia emulation. The comparison is based on state-space models of the considered control schemes, which are linearized and utilized for eigenvalue-based analysis. Starting from a comparison of the three schemes with manually tuned controller parameters, it is shown that the current controlled VSM can be unstable for strong grid conditions, while the df/dt-based control becomes unstable when the grid impedance is high. Thus, an iterative tuning algorithm based on eigenvalue parametric sensitivities is applied to investigate how much the time-response and damping of the critical modes can be improved. Limitations to the dynamic performance are identified by participation factor analysis of the critical modes. The results demonstrate that all the investigated schemes can be stable for a wide range of operating conditions, but with inherent differences in the inertial response.

Direct Cell-to-Cell Voltage Equalizer Using Capacitively-Isolated Parallel-Resonant Converter for Series-Connected Energy Storage Cells

Abstract: Direct cell-to-cell voltage equalizers have been proposed for series-connected energy storage cells, such as lithium-ion batteries and electric double-layer capacitors (EDLCs). Conventional direct cell-to-cell voltage equalizers, however, require a transformer for isolation, resulting in increased circuit volume. In this paper, a capacitively-isolated parallel-resonant converter is proposed to miniaturize the circuit volume by employing capacitive isolation, instead of a bulky transformer. No feedback control is necessary for the proposed converter to limit its currents under desired levels, and safe operation is feasible even when some cell voltage is 0 V because of the inherent constant current characteristic of the parallel resonant converter at a fixed switching frequency. A 1.0 W prototype and cell selection switch module for twelve cells connected in series were built, and an equalization test for EDLCs was performed from voltage imbalanced condition. The voltage imbalance was eliminated by the proposed equalizer, demonstrating the efficacy of the equalization performance.

SCC Equivalent Resistance: The Relationship for Complementary Buck and Boost and Accurate Calculation for 2-Phase Converters

Abstract: This paper makes the following contributions to Switched Capacitor Converter (SCC) equivalent (output) resistance analysis. First, it suggests the relationship between equivalent resistances of complementary buck and boost SCC: equivalent resistance of a boost SCC equals that of its buck counterpart times squared boost voltage Target Ratio (Voltage Conversion Ratio). Another contribution is equivalent resistance accurate calculation methodology for an arbitrary 2-phase SCC.