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Review and comparison of methods for limiting leakage currents in single-phase transformerless PV inverter topologies

Kołodziejski Wojciech, Jasielski Jacek, Kuta Stanisław W., Szerszeń Grzegorz, Machowski Witold

Science, Technology and Innovation

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2022

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Vol. 16, no. 3-4

1--19

EN

Transformerless inverters are widely used in different photovoltaic nonisolated ac module applications, mainly in grid-tied photovoltaic (PV) generation systems, due to the benefits of achieving high efficiency over a wide load range, and low cost. Various transformerless inverter topologies have been proposed to meet the safety requirement of low ground leakage currents, such as specified in the VDE-4105 standard and low-output ac-current distortion. Topology modifications of transformerless full bridge inverters are designed to balance and maintain a constant common mode output voltage, thereby eliminating or reducing leakage currents. This article reviews and compares the different methods for limiting leakage currents in known topologies of the full-bridge transformerless inverters, such as: H4, H5, H6, HERIC, and their improvements. The main topologies and strategies used to reduce the leakage current in transformerless schemes are summarized, highlighting advantages and disadvantages and establishing points of comparison with similar topologies. To compare the properties of different medium to high power inverters, PV inverter topologies were implemented using IGBTs and tested with the same components, same simulation parameters in PSPICE to evaluate their performance in terms of energy efficiency and leakage current characteristics. The detailed power stage operating principles, extended PWM modulator, and integrated universal gate driver with galvanic isolation in the transmission path of control signal for all IGBTs of the inverter, as well isolated and floating bias power supply for gate drivers are described.

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Falownik trójfazowy ze zmiennym algorytmem sterowania

Szerszeń Grzegorz, Zygadło Damian

Science, Technology and Innovation

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2021

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Vol. 14, no. 3-4

1--11

PL

Wpracyprzedstawionobudowę trójfazowegoprzemiennika częstotliwości zmożliwościąwyboru typu modulacji PWM oraz płynną zmianą częstotliwości sygnału modulowanego.Wpraktyczny sposób zrealizowano różne algorytmy sterowania falownikaw tymsamymukładzie sprzętowym zwykorzystaniemprocesora STMARMCortexM3. ZastosowaniemodulacjiTHIPWMpozwoliło zmniejszyć zawartośćharmonicznychw sygnalewyjściowymi efektywniewykorzystaćmożliwości źródła zasilania. Układ posiada możliwość wyboru jednego z dwóch algorytmów sterowania skalarnego, z opcją kompensacji wpływu rezystancji stojana na moment obrotowy wału silnika w początkowym zakresie charakterystyki sterowania liniowego przy stałym stosunku napięcia do częstotliwości. Badania potwierdziły, że najkorzystniejszym typem modulacji PWM w tym układzie jest modulacja jednobiegunowa dwubrzegowa.Wykorzystanie metodyTHIPWM, skutkowało zyskiem amplitudy podstawowej harmonicznej napięcia wyjściowego dla trójfazowego trybu pracy falownika względem metody SPWM. Uzyskano także odpowiednią precyzję kroku regulacji częstotliwości, a rezultaty badań potwierdziły funkcjonalność przemiennika.

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The paper presents the construction of a three-phase frequency converter with the possibility of choosing the type of PWM modulation and a smooth change of the frequency of the modulated signal. In a practical way, various inverter control algorithms were implemented in the same hardware system using the STM ARM Cortex M3 processor. The use of THIPWM modulation allowed to reduce the harmonic content in the output signal and effectively use the possibilities of the power source. The system can choose one of two scalar control algorithms, with the option of compensation for the influence of the stator resistance on the motor shaft torque in the initial range of the linear control characteristic at a constant voltage to frequency ratio. The research confirmed that the most advantageous type of PWM in this system is unipolar double-edge modulation. The use of the THIPWM method resulted in a gain in the amplitude of the fundamental harmonic of the output voltage for the three-phase inverter operation mode compared to the SPWM method. The appropriate precision of the frequency control step was also obtained, and the test results confirmed the functionality of the converter.

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The 8AE-PD computer measurement system for registration and analysis of acoustic emission signals generated by partial discharges in oil power transformers

Witos Franciszek, Opilski Zbigniew, Szerszeń Grzegorz, Setkiewicz Maciej

Metrology and Measurement Systems

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2019

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Vol. 26, nr 2

403--418

EN

A computer measurement system, designed and built by authors, dedicated to location and description of partial discharges (PD) in oil power transformers examined by means of the acoustic emission (AE) method is presented. The measurement system is equipped with 8 measurement channels and ensures: monitoring of signals, registration of data in real time within a band of 25-1000 kHz in laboratory and real conditions, basic and advanced analysis of recorded signals. The basic analysis carried out in the time, frequency and time-frequency domains deals with general properties of the AE signals coming from PDs. The advanced analysis, performed in the discrimination threshold domain, results in identification of signals coming from different acoustic sources as well as location of these sources in the examined transformers in terms of defined by authors descriptors and maps of these descriptors on the side walls of the tested transformer tank. Examples of typical results of laboratory tests carried out with the use of the built-in measurement system are presented.