Pertti Silventoinen

Implementing sliding mode control for buck converter

The theory of sliding mode control (SMC) to switch mode power supplies have been widely investigated in literature, but most of the papers have focused on the theoretical aspects of this control without any practical implementations. This paper links the theory to practical power supply design. Analysis and experimental study of buck converter is presented, and nonlinear state feedback control is derived to achieve desired output voltage. The paper focuses on modelling a control circuit in Matlab/Simulink/spl trade/ and implementing it to the buck converter. Next, a prototype with SMC is build up. The output voltage and inductor current of the both models are compared in steady state mode and under line and load variations. The efficiency is also calculated from the measurements made with the prototype. All these measurements showed advantageous results.

Decoupled Vector Control Scheme for Dual Three-Phase Permanent Magnet Synchronous Machines

Dual three-phase electric machines have many advantages compared with conventional three-phase machines. However, the properties of such machines present challenges for current control that make it difficult to produce sufficient performance for the electric drive. This paper introduces an improved vector control scheme for dual three-phase permanent magnet synchronous machines. The study includes detailed solutions for key parts of the control such as reference frame transformations, decoupling of the current control loops, and modulation. The performance of the suggested control scheme is evaluated using finite-element analyses and experimental results. The results show that the scheme can produce desired dynamics for the current control and guarantees balanced current sharing between the winding sets. In addition, the proposed solution is capable of reducing current harmonics produced by the internal structure of the machine. This problem is, however, only partly solved since complete elimination of harmonic components is not achieved. Nevertheless, the suggested control scheme overcomes many of the disadvantages found with other control solutions. Improved control performance allows the full benefits of dual three-phase drives to be utilized even in demanding applications.

Short-Circuit Protection in a Converter-Fed Low-Voltage Distribution Network

The short-circuit protection of a low-power converter-fed low-voltage dc distribution network is investigated. In a public distribution network, the short-circuit protection is implemented by using fuses and circuit breakers, which may require a current that is over ten times the nominal currents of low-power dc/ac converter units to satisfy the recommendations. In the paper, the operation of the converter in a short circuit is studied, and the control scheme for the short-circuit current control and the fault ride through operation is proposed. The operation of the short-circuit control scheme is verified by measurements. To overcome the problem of high fault current injection, alternative short-circuit protection realizations that are based on a simple low-current compact circuit breaker (but are not approved in standards) are proposed and demonstrated by measurements.

A Review of Microstrip T-resonator Method in Determination of Dielectric Properties of Printed Circuit Board Materials

When designing devices at microwave frequencies, the characteristics of printed circuit board materials should be well known in order to attain exact functionality. The characterization can be carried out for example with T-resonator test method. In this paper, microstrip T-resonator test method is analyzed. The analysis is based on literature search and experimental research, and the practicable calculation methods are introduced. The introduced modifications provide more precise calculation improving the accuracy of the method. The modifications also enable the determination of dielectric properties of high loss printed circuit board materials at broad frequency and temperature ranges

Variable-Frequency Phase Shift Modulation of a Dual Active Bridge Converter

In this paper, a variable-frequency modulation method for a dual active bridge converter is introduced. The proposed method ensures zero-voltage switching over a wide power range with a minimal circulating current. Unlike previously presented modulation schemes, this modulation method can also be used for half-bridge variants of a traditional dual active bridge converter. The modulation method is given in a closed form, which makes it easy to apply in practice. Further, the phase drift phenomenon is discussed, and a simple phase drift compensation scheme is presented. Finally, a detailed analysis of the proposed modulation method is provided and its feasibility is verified by measurements.

Dual three-phase permanent magnet synchronous machine supplied by two independent voltage source inverters

This paper investigates a dual three-phase permanent magnet synchronous machine supplied by two independent three-phase voltage source inverters (VSIs). Dual three-phase machines have many important advantages compared with their conventional three-phase counterparts. Instead of six-phase converters and special vector controls, it would be a very interesting alternative to supply these machines by two conventional three-phase VSIs since they are readily commercially available. This paper shows that the proposed supply method can be used successfully although it suffers from a decrease in the dynamic performance and an error in the estimation of torque. On the other hand, two independent VSIs do not cause low-frequency current harmonics and guarantee balanced current sharing between the winding sets thus avoiding the two most common problems with dual three-phase machines. Experimental results are provided to verify the conclusions. The results suggest that the simple supply method of two conventional VSIs could be a feasible alternative for many industrial applications.

Effects of Switching Asymmetry on an Isolated Full-Bridge Boost Converter

The effects of switching asymmetry and flux walking on an isolated current-fed full-bridge boost converter are presented with two different secondary configurations: a voltage doubler (VD) and a diode bridge (DB). The results show that a drop in the converter efficiency is clearly visible when there are switching asymmetries in the DB configuration, whereas the VD configuration is more tolerant of switching asymmetries because of its inherent capability to oppose flux walking.

Research Site for Low-Voltage Direct Current Distribution in a Utility Network—Structure, Functions, and Operation

This paper introduces a research site for a low-voltage direct current (LVDC) distribution system. The research site was established to enable practical studies concerning different areas of the LVDC distribution. Because the LVDC distribution is a novel approach to public electricity distribution, the objective is to combine a fully functional LVDC system and a flexible research platform, where various measurements and tests can be conducted. The scope of this paper is to discuss the design, structure, functionalities, and operation of the site. Experiences of use and measurement results are provided to demonstrate the major functionalities and other important system properties. Finally, future research tasks and the development of the site towards the LVDC μGrid are presented.

Online Estimation of Double-Star IPM Machine Parameters Using RLS Algorithm

Accurate and updated knowledge of the electric machine parameters provides benefits in many applications, such as model-based control methods. This paper presents an online parameter estimation method for double-star interior permanent-magnet (IPM) machines supplied with voltage-source inverters (VSI). The estimation method is based on a decoupled D-Q model of the machine and a recursive least-squares (RLS) algorithm. Initial machine parameters are estimated at a standstill. Then, in the rotating operating state, the inductances and the flux linkage produced by the PMs are updated. The estimation in the operating state is performed with a flux-linkage-based approach. The experimental results are compared with the corresponding values obtained from finite-element analyses. The results show an acceptable agreement and demonstrate the feasibility of the estimation scheme to estimate the parameters of double-star PM machines. The parameters are validated by comparing experimental and simulated open-loop responses and steady-state torques.

A new method to measure dielectric constant and dissipation factor of printed circuit board laminate material in function of temperature and frequency

In this article, a new method to measure the values of dielectric constant and dissipation factor of printed circuit board laminate material in function of temperature and frequency is presented. The method is based on the use of microstrip ring resonator structures and a climate chamber. The presented method is experimentally tested at frequency range from 1 GHz to 10 GHz and at the temperature range from -30/spl deg/C to 105/spl deg/C. With the presented method, frequency properties of different laminate materials and coatings can be measured at wide frequency and temperature range.