Vladimir Katic

Permanent Magnet Synchronous Generator Cascade for Wind Turbine Application

This paper proposes an energy conversion system for a wind turbine comprising a grid connected permanent magnet synchronous generator and a 20% rated series converter located in its star point. It models the complete system and focuses on the series converter control whose primary function is the active damping of the generator. In addition, this paper addresses the topic of the dc bus voltage control and the dc capacitance sizing of the series converter. Finally, it validates the performance of the proposed system by means of system simulation.

Power Quality Problems Compensation With Universal Power Quality Conditioning System

The aim of this paper is to present a universal power quality conditioning system (UPQS) named after unified power quality conditioner, which is extended by adding a shunt active filter at the load side. Its main purpose is to compensate for both supply voltage and load current imperfections, such as: sags, swells, interruptions, imbalance, flicker, harmonics, reactive currents and current unbalance. Such system has better harmonic compensation characteristic, since there are no problems associated with passive filter operation. Converter and control analysis is presented, together with results showing the UPQS modes of operation

HIL Evaluation of Power Flow Control Strategies for Energy Storage Connected to Smart Grid Under Unbalanced Conditions

This paper proposes two power flow control algorithms for a grid-connected voltage source converter used as part of the energy storage for a smart grid under unbalanced voltage conditions. Both algorithms are improvements of the dual vector current control algorithm (DVCC). The first proposed algorithm, DVCC_CL, optimizes the method of limiting phase currents for the duration of voltage unbalance. The second proposed algorithm, DVCC_HB, provides high bandwidth control of active and reactive power. Which of the two proposed algorithms is the better choice depends on the grid code requirements and the constraints imposed by the particular energy storage system which the inverter connects to the grid. The operation of both algorithms was verified within the framework of an ultralow-latency hardware-in-the-loop emulator, which makes accurate analysis of converter behavior safe and easy for any grid conditions.

Ultralow-Latency Hardware-in-the-Loop Platform for Rapid Validation of Power Electronics Designs

This paper introduces a unified approach to the validation of power-electronics (PE) control hardware, firmware, and software designs. It is based on a scalable application-specific ultralow-latency (ULL) digital processor core. The proposed ULL processor core simulates PE converters and systems comprising multiple power converters with a fixed 1-μs simulation time step and latency, regardless of the size of the system. Owing to its ULL, the proposed platform enables the fully automatic testing and validation of the complete PE design comprising component safe-operating-area validation, system protection, firmware, and software implementation as well as overall system performance optimization.

Application-oriented comparison of the methods for AC/DC converter harmonics analysis

Fourier transform (FT) is the most widely used tool for voltage and current waveform analysis. Nevertheless, it has certain drawbacks for time-varying signals analysis. Therefore, a need for another analysis technique appears. windowed FT, wavelet transform, and modulated lapped transform were considered in this paper. Comparison based on practical application shows the advantages of the last one. As an example, it has been applied for ac/dc converter input current harmonics analysis.

Development of High-Reliability EV and HEV IM Propulsion Drive With Ultra-Low Latency HIL Environment

This paper proposes an improved and robust method of minimizing the error in propulsion-drive line-currents that are reconstructed from a single dc-link current measurement. The proposed algorithm extends and then shortens the relevant phase pulse-widths in order to provide optimal sampling of the dc-link currents in two consecutive pulsewidth modulation (PWM) periods. The proposed PWM pattern control enables an improved sampling method which cancels offset jitter-like waveform errors present in all three reconstructed line-currents, which is due to a specific combination of nonsimultaneously sampled dc-link current and line-current PWM ripple. The improvement in induction motor drive accuracy using a single current-sensor and no shaft sensor (as proposed in this paper), over that of conventional methods, is shown. Thanks to an ultra-low latency hardware-in-the loop (HIL) emulator, the proposed algorithm, its implementation on a DSP processor, code optimization and “laboratory” testing were all merged into one development step. In order to perform final tests of the proposed current-reconstruction algorithm and to verify the usefulness of the developed HIL platform by means of comparison, experimental results obtained on a real hardware setup are provided.

Ultralow Latency HIL Platform for Rapid Development of Complex Power Electronics Systems

Prototyping and verification of complex power electronics (PE) systems and control algorithms is a laborious and time-consuming process. Even when a low-power hardware model is assembled, it enables only a limited insight into the large number of operating points; changes in system parameters regularly demand hardware modifications and always there is the risk of hardware damage. The ultralow-latency Hardware-In-the-Loop (HIL) platform proposed in this paper combines the flexibility, accuracy, and ease of use of state-of-the-art-simulation packages, with the response speed of small power-hardware models. In this way, PE systems-optimization, code-development, and laboratory-testing can be combined into one step, which dramatically accelerates the pace of product prototyping. Low-power hardware-models also suffer from nonscalability, because some parameters such as electrical machine inertia cannot be properly scaled. However, HIL enables control prototyping that covers all operational conditions. In order to demonstrate HIL-based rapid development, the verification of an active damping algorithm for a permanent magnet synchronous generator (PMSG) cascade is performed. Two goals are set in this paper: to verify the developed HIL platform by means of comparison with a low-power hardware setup and then to emulate the real, high-power system in order to test the active damping algorithm.

Online control of current-source-type active rectifier using transfer function approach

Current-source topology AC/DC converters (buck converters) operated using pulsewidth modulation have significant drawbacks in lack of line current control and AC-side filter damping. Also, an AC-side filter is usually overrated in order to keep harmonic distortion under imposed limits. Discontinuous current at converter line inputs disables the use of current control techniques known from control of voltage-source converters. In order to overcome these problems, an online control method for the buck converter is presented in this paper. This method is based on the AC filter transfer function approach. Such an approach enables a novel solution for line-side filter optimization in the case of hysteresis line current control. This method leads to a filter with minimal apparent power (cost) and the fast and accurate converters control response. Furthermore, a line current estimation method was developed. It uses only one current sensor at the converter DC side in order to estimate power supply currents. Suggested methods were numerically and experimentally verified.

Control of Multilevel Converter Driving Variable Speed Wind Turbine in Case of Grid Disturbances

This paper proposes modified dual vector current control (DVCC) for the wind turbine application. As in case of conventional DVCC, it fulfills requirements for average unity power factor with suppressed oscillations in active power flow. However, uncontrolled increase in converter output current under unbalanced grid voltage conditions is prevented through imposing limit in its magnitude. Multilevel back-to-back converter is used in order to achieve full control of the turbine, as well as better power quality and lower torque and grid current oscillation

Advanced laboratory setup for control of electrical drives as an educational and developmental tool

A new advanced laboratory setup has been developed on the Faculty of Technical Sciences, Group of Power Electronic and Drives. The idea behind this laboratory setup is to establish a base for research and development work in the field of electrical drives and digital control. It serves as an educational tool for MSc and PhD students, as well as the research foundation with its sophisticated hardware and software arrangements. Basis of the hardware consists of dSPACE platform and its corresponding boards, alongside with industrial converters with custom-made control board, for the development of own personal control techniques. Corresponding software is RealTime Interface block-set and Matlab/Simulink. This paper aims to show a part of research work done on this setup, thus describing its educational and developmental potential.