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This paper presents an assessment of the levels of total harmonic distortion (THD) in buck-boost DC-AC converters using triangular wave and saw-tooth unipolar based-modulation schemes. This paper seeks to identify a better technique for mitigating the total harmonic distortion on buck-boost DC-AC converters under unipolar carrier-based modulation schemes. This was achieved by subjecting the buck-boost DC-AC converter under triangular wave-based and saw-tooth based-unipolar modulation schemes. The voltage and current output of the buck- boost DC-AC converter under each scheme was analysed using a power GUI Fast Fourier Transform (FFT) analytical tool resident in the MATLAB Simulink environment unlike with the conventional scheme of computing the percentage of THD. The test system was obtained by a combination of DC-DC buck-boost converter, H-bridge based-insulated unipolar gate transistors, and a logic control unit. It was realized that THD of 0.2865%, peak output voltage of 294.1V and current of 9.805A were obtained by using the saw-tooth based-unipolar modulation scheme, whereas a THD of 0.1479%, peak output voltage of 297.4V and current of 9.53A were obtained by using the triangular wave based-bipolar modulation scheme on the same Buck-boost DC-AC converter circuit. The results imply a high power factor utilization and low power loss in the triangular wave based-unipolar modulation scheme compared to the saw-tooth based-unipolar modulation technique for improving the performance characteristics of the buck-boost converter system. This study showed that power drives and heavy load machines based-power electrical loads are required to use the saw-tooth based-unipolar modulation (STBUM) scheme for high current and low THD%, whereas sensitive power electrical loads such as hospital equipment and communication industries based-power electronic devices are required to use the triangular wave-based unipolar modulation (TWBUM) scheme due to low current and THD%.

This paper presents a headroom-based optimization for the placement of distributed generation (DG) in a distribution substation. The penetration limits of DGs into the existing distribution substations are often expressed as a function of the feeder’s hosting capacity (headroom). Therefore, it is important to estimate the reliability of the network's operation as well as that of the limits imposed by the power quality standards by evaluating of the hosting capacity (headroom) of the existing distribution feeder substation. This study aims at developing a novel algorithm for positioning a bus with permissible headroom capacity for DG positioning without causing voltage violations but maximizing the active power supply. Since DG increases short-circuit faults, the algorithm is useful for utility companies to select feeder substations that have permissible headroom capacity for DG installation and thus, contributing to reducing high DG penetration in the network. The modeling and optimization were carried out the Power System Software for Engineers (PSS/E) environment using the IEEE 14-bus test system. The results obtained from the case study show that only two (2) feeder substations out of fourteen (14) have the permissible headroom capacity for DG connections.

This paper presents a novel modulation scheme known as the nonzero staircase modulation scheme for switching DC-DC boost converters. This modulation scheme generates two distinct pulse trains/firing signals when a 50 Hz nonzero staircase modulating signal is compared with a 1.5 kHz triangular wave signal. Unlike the conventional modulation schemes, the proposed novel modulation scheme provides two distinctive trains of pulse-width modulated signals for mitigating low and high harmonics. It also possesses 0.56% total harmonic distortions (THD) of the output voltage waveform system, a power output of 4591 W, and THD of 1.12% in the DC-DC boost converter system. It has a simple design and low power loss of 209 W. The proposed scheme enables the single switch boost DC-DC converter used to have an efficiency of 96%. The proposed scheme can be applied in single switch or double switch boost DC-DC converter based-hospital equipment.

This paper presents a low-cost printed circuit board (PCB) design technique and processes using ferric chloride (𝑭𝒆𝑪𝒍𝟑) solution on a metal plate for a design topology. The PCB design makes a laboratory prototype easier by reducing the work piece size, eliminating the ambiguous connecting wires and breadboards circuit errors. This is done by manual etching of the designed metal plate via immersion in ferric chloride solutions for a given time interval 0-15mins. With easy steps, it is described on how to make a conventional single-sided printed circuit board with low-cost, time savings and reduced energy from debugging. The simulation and results of the printed circuit is designed and verified in the Multisim software version 14.0 and LeCroy WJ35Aoscilloscope respectively. Keywords: Etching, Ferric Chloride, Insertion, Multisim, Metal Plate, Printed Circuit Board

This paper presents the analysis, modeling, simulation, and implementation of a high performance DC-to-AC (DC-AC) converter. The system comprises of a combination of DC power source, stress less DC-to-DC (DC-DC) voltage converter, two snubberless power switches, and control unit. The system is portable, has a two-stage input voltage transformation and amplification with no transformer and occupies less space unlike the classical two-stage inverter systems. In addition, the system produces a constant DC boosted voltage with less stress on both the source and DC storage capacitor which are not found in conventional converters. The proposed power electronic converter system produced the following results: pure sine voltage and current waveforms, total harmonic distortion (THD) of 4.294%, power output of 5740W, efficiency of 98.9%, power loss of 60W and fast dynamic response. The target areas of applications of the proposed converter are in medium and small scale industries.

This paper presents an improved conventional diode-clamped multilevel inverter using non-zero triangular-based unipolar modulation scheme. The proposed scheme is meant to reduce the number of carrier waves, minimize the circuits of modulation scheme and obtain stabilized output voltage waveforms. Non-zero triangular-based unipolar modulation scheme is actualized by using two zero-free triangular wave carriers and two modulating sinewaves for line-to- line five level output voltage waveforms in single phase full bridge diode-clamped multilevel inverter unlike conventional multicarrier sinusoidal pulse width modulation that uses four triangular waves and one modulating sinewave for the same inverter type. The proposed system also used microcontroller in the combinational of its wave signals in order to generate the appropriate triggering signals for switching the power semiconductor switches. The proposed system has the following features: (i) It produces two distinct triggering trains (W1 and W2) meant to reduce the low and high harmonics unlike conventional modulation techniques (ii) All its carrier waves operate in continuous current mode which makes it unique from other multicarrier and other related modulation schemes (iii) it has low component counts. The proposed scheme on the conventional diode-clamped inverter produced the following results: voltage and current with total harmonic distortions of 0.4547%, stabilized 400V output voltage and 20A output current, probability results at each level of voltage and current occurrences are 0.10, 0.25, 0.25, 0.75 and 0.90; power output of 80kW, low component counts of modulation circuit scheme and experimental prototype.

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