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Robert Stala

Abstract

The flying-capacitor (FC) topology is one of the more well-established ideas of multilevel conversion, typically applied as an inverter. One of the biggest advantages of the FC converter is the ability to naturally balance capacitor voltage. When natural balancing occurs neither measurements, nor additional control is needed to maintain required capacitors voltage sharing. However, in order to achieve natural voltage balancing suitable conditions must be achieved such as the topology, number of levels, modulation strategy as well as impedance of the output circuitry. Nevertheless this method is effectively applied in various classes of the converter such as inverters, multicell DC-DC, switch-mode DC-DC, AC-AC, as well as rectifiers. The next important issue related to the natural balancing process is its dynamics. Furthermore, in order to reinforce the balancing mechanism an auxiliary resonant balancing circuit is utilized in the converter which can also be critical in the AC-AC converters or switch mode DC-DC converters. This paper also presents an issue of choosing modulation strategy for the FC converter due to the fact that the natural balancing process is well-established for phase shifted PWM whilst other types of modulation can be more favorable for the power quality.

Open access

Adam Henryk Kawa and Robert Stala

Abstract

This paper presents the research results of a multilevel switched capacitor DC-DC converter (MLSCC). The converter, for power electronic applications, can operate in ZCS mode by utilizing resonant circuits for recharging the switched capacitors. The main focus of this article is an in-depth original analysis of the waveforms and the converter voltage ratio. The concept of the converter is verified by simulation results of the circuit in MATLAB/Simulink Sim Power Systems. The formulas given in the mathematical analysis are evaluated for example parameters of the components with the use of numerical approach in MATLAB software. Plot sets are presented in order to judge the influence of the parameters on converter performance. All non-expected relations are explained based on mathematical analysis. The possibilities of the design optimization are identified and presented based on the anticipated results. The present analysis is important for the converter design process and can be used for numerical multi-object optimization to further improve the converter design.

Open access

Jakub Hachlowski and Robert Stala

Abstract

This paper presents a novel concept of a circuit for voltage balance of three series-connected capacitors or batteries, as well as the research results. The problem is related to the control of voltage sharing on series capacitors, supercapacitors or battery banks in energy storage systems or direct current (DC)-link of four-level neutral-point-clamped inverters. The proposed circuit is a switched-capacitor (SC) resonant converter composed of a single capacitor and seven transistor switches. Control of the converter makes it possible to transfer energy between any capacitors, by switching selected transistors. This paper presents the basic concept of the converter, an analysis of control strategies and the simulation results for various cases of voltage balancing.

Open access

Adam Kawa and Robert Stala

Abstract

The paper presents investigation results of the natural balancing phenomena in the flying-capacitor SEPIC converters. The SEPIC converters topologies can be reconfigured to the flying-capacitor topology. Owing to this modification the advantageous increase of frequency of the current in the chokes and the decrease of semiconductors voltages can be achieved which is shown in this paper. Similarly to other multilevel flying capacitor topologies the adequate voltage sharing of the flying capacitors is an important issue for safe operation of the converter. The paper focuses on the analysis of the flying capacitor voltages balancing in the converter by natural currents as well as by the application of the additional RLC balancing booster. The paper proves that the natural balancing can be achieved by the specific application of the balancing circuit in the flying-capacitor SEPIC topology and proves the specific differences in the balancing process by natural currents of converter and with the usage of the balancing circuit. An operation of the converter with the balancing circuit and the natural balancing ability is studied here.

Open access

Robert Stala, Adam Penczek, Andrzej Mondzik and Łukasz Stawiarski

Abstract

This paper presents a novel, low-complexity method of simulating PV source characteristics suitable for real-time modeling and hardware implementation. The application of the suitable model of the PV source as well as the model of all the PV system components in a real-time hardware gives a safe, fast and low cost method of testing PV systems. The paper demonstrates the concept of the PV array model and the hardware implementation in FPGAs of the system which combines two PV arrays. The obtained results confirm that the proposed model is of low complexity and can be suitable for hardware in the loop (HIL) tests of the complex PV system control, with various arrays operating under different conditions.

Open access

Zbigniew Waradzyn, Robert Stala, Aleksander Skała, Andrzej Mondzik and Adam Penczek

Abstract

This paper presents the results of experimental research of a resonant switched capacitor voltage multiplier in a cost-effective topology (CESCVM) with a limited number of active switches. In the charging mode of the switched capacitors, the converter utilizes only one active switch and a required number of diodes. Therefore, the cost of the converter is decreased as compared with that of a classical SCVM converter, owing to a lower number of switches and gate driver circuits, as well as a smaller PCB area. Moreover, the CESCVM has simpler control circuits and higher reliability. This paper presents the original experimental results of the operation of the CESCVM converter. A concept of the bootstrap supply of gate drivers of the flying switches is also examined.