Jaroslaw Michalak

DC-link voltage balancing method for a hybrid asymmetric multilevel converter

The paper presents the dc-link voltage balancing method for a five-level hybrid asymmetric multilevel converter based on a neutral point clamped (NPC) converter with H-bridge (HB) converters. The considered converter, which is referred to as NPC-HB, is treated in this paper as a modification of the classic three-level NPC converter. It improves the harmonic performance of output voltage compared to the NPC converter. This improvement is made by increasing the number of levels in the converter output voltage. Nevertheless, due to the use of floating H-bridge converters inside the NPC-HB topology, the dc voltage balancing method is implemented. Basing on the converter ac side current and HB converter dc link voltage, the proposed method modifies the PWM modulation scheme in both NPC and HB converters. This modification is applied to each switching period while the converter output voltage reference is kept unchanged. Such modulation scheme is characterized as robust and guaranteeing the low harmonic content in the output voltage. Other dc voltage balancing methods of the hybrid NPC-HB converter are compared in this paper. The proposed method is experimentally verified.

Comparison of SMES and ScES based power conditioning systems

The selection of the less expensive power conditioning system (PCS) is the aim of the work where two types of PCS are taken into consideration. The first type of PCS is based on superconducting magnetic energy storage (SMES) while the second one is based on supercapacitor energy storage (ScES). The comparison is based on installed power as the criterion. An illustrative example is given in the work

Analysis of thyristor switch in power conditioning system with SMES

Ensuring high level of power quality (PQ) is one of most important issues in supplying in industry loads. There exist some critical types of loads that should be protected from any voltage disturbance. If any voltage disturbance (like voltage sag or dip) occurs an alternative energy source is used to ensure constant voltage amplitude across protected load. In described power conditioning system (PCS), power electronic system is connected in parallel to group of protected loads. The PCS together with protected loads have to be disconnecting from the mains in the case of voltage sag or dip occurs. Disconnection is necessary, if any voltage disturbance occurs, to prevent from delivering energy to low impedance part of power system (the mains in such case) from energy storage that is contained in the PCS (in this situation high temperature superconducting magnetic energy storage (SMES)). In described system breaking the connection between the mains and the load takes place thanks to the thyristor switch (TS). Disconnection and reconnection modes of operation of the PCS are particularly described and analysed in the paper. To obtain relatively low turn off time of thyristor switch a new method of controlling the PCS has been proposed that can assist turning off process of the TS and decreasing turn off time. The resynchronisation of the load voltage and the mains voltage of the PCS is also presented in the paper. It is used to limit the amplitude of the mains current after reconnection process. Influences of resynchronisation and reconnection processes on load voltage are also analysed. To proof correctness of designed controller the simulation and experimental results have been presented and discussed in the paper

Application of System on Chip (SoC) devices for the design of a smoke detector working with megapixel image streams

The paper discusses the application of System on Chip devices for processing Megapixel video streams. The domain of image processing using high resolution images is very demanding in the scope of calculating power and frequently exploits special processing hardware. The progress of integration technology brings about SoC which are capable of meeting such processing demands. Characteristics of FPGA and DSP based systems are assessed. A concise survey of chip solutions is presented and a pair of representative systems is chosen for comparison of their properties. The design of a smoke detection system is used for evaluating the advantages and drawbacks of using such SoC solutions. Almost identical image processing algorithms are implemented in the case of FPGA and DSP. Both solutions meet the image processing requirements and are suitable for real time processing. FPGA based solution is much faster as it uses pipelining for improving the utilisation of scarce memory resources.

Study of adaptive proportional observer of state variables of induction motor taking into consideration the generation mode

The paper presents problems related to the design and the stability of adaptive proportional observer which is used in sensorless, field oriented control system for estimation of magnetic flux and motor speed of induction motor. The gain matrix of the observer was determined by pole placement method in such a way, that the observer without adaptation has only real poles. It has been shown that adaptive proportional observer is stable also during generation mode of operation of the motor. The paper presents the results of simulation and laboratory tests.