A Generalized Approach to Analysing a Class of Passively Soft-Switched PWM DC-DC Converters

In this paper, a generalised approach to the analysis of a class of passively soft-switched PWM DC-DC converters is presented. The circuit cell that gives this class of converters its passively soft-switched characteristics is first introduced. The use of this circuit cell to transform the basic hard switched converters (buck, boost, bucklboost, Cuk's, Sepic and Zeta) into their varied passively soft-switched PWM topologies is illustratively presented. A generalised analysis representative of all the soft-switched converter types in the class is carried out

A Microprocessor-Based Control, Scheme for a PWM Voltage-Fed Inverter with an Induction Heating Tank Load

In this paper, the flexibility of programmed control logic is exploited in the close loop control of a PWM thyristor voltage fed inverter supplying an induction heating tank load. The microprocessor used in the control is the MC6809 to which is interfaced the SY6522 versatile interface adapter (VIA). The microprocessor-based scheme performs the dual function of generating the thyristor gating signals as well as estimating and applying control actions to maintain the load power factor at unity and the power delivered to the load at a desired set-point value. The schemed also provides power circuit over-current and over-voltage protection against adverse changes in the inverter input supply and the load. The estimation  of the control variables of the control scheme proportional plus integral controllers constitute the main control program while the application of thyristor gating signals and closed loop control actions are carried out in response  to interrupts external to the microprocessor unit. Illustrative steady state and transient circuit of an experimental model of the induction heater are given

Modes of Current Conduction in 2-Pulse PWM AC/DC Converter

The paper reports the result 0f a study on the load current conduction modes in the one phase two-pulse PWM AC/DC converter. The various load current conduction modes are identified by the signs of the instantaneous load current values at selected load voltage discontinuity points under an assumed continuous load current operation over relevant ranges of the modulation index. From the derived load current conduction equations, boundary curves are plotted to illustrate the converter current conduction characteristics that help predict converter performance under given modulation index and load conditions. This work provides first hand information on current conduction modes in the single pulse modulation of the one phase full bridge converter and the analysis approach used provides more detailed information on load current conduction than the approach adopted in (2, 3, 4) for the phase controlled converter

Solar-Based Boost Differential Single Phase Inverter

This paper depicts about a power conversion circuit of a Pulse-width modulated (PMW) voltage source inverter known as a Solar-based boost differential single phase inverter. The total harmonic distortion of 67.12% found in an open loop Solar-based boost differential inverter is reduced down to 22.37% in closed loop system with the aid of Proportional –integral-Differential (PID) voltage controller. The transient stage of the proposed system takes conical shape before it reaches its steady state.   The core characteristics of this type of inverter are:  it engenders an ac output voltage that is greater than the dc voltage which is not obtained in conventional inverter, it trims down the many stages of power conversions found in other boost converters to one stage, it mitigates the ripple contents of the input voltage and current concurrently and finally, it is portable. This research also shows the disparity between the simulated results of open loop and closed loop of boost differential inverter systems. The dc power source is photovoltaic cell. The maximum power point tracker is in-cooperated in capturing the maximum power from the sun. The proposed topic has its applications in homes, offices and more in industries

Modeling and Analysis of a Three-Phase Solid-State Var Compensator (SSVC)

The problems associated with the flow of reactive power in transmission and distribution lines are well known. Several methods of var compensation have been applied in solving these problems. This paper examines the performance of a three-phase solid-state var compensator employed in the power system for reactive power compensation. The principal component of this device is a three-phase pulse-width-modulated voltage source inverter. A mathematical model of the inverter is derived and then used for the transient analysis. Optimization of the ac input power factor can be achieved by adjusting the angle difference between the inverter fundamental output voltage and the utility supply voltage. The open-loop frequency responses obtained show a very stable, high speed performance in the frequency range of interest

Performance Characteristics of an Armature Voltage Controlled D.C. Motor

In this paper, the performance study of a separately excited d. c. motor whose speed is controlled by armature voltage variation is presented. Both the open loop and the closed loop steady state and transient characteristics are reported. The speed controllers considered in the closed loop mode are the proportional and the proportional plus integral types. To each of these two control arrangements is added an inner current controller loop. Using developed motor equations, the performance characteristics of a test motor are obtained by digital computer analysis. The results show that closed loop operation, with appropriate control gains, give improved speed regulation and response characteristics for the d. c. drive system

New Topology For Single-Phase, Three-Level, SPWM VSI with LC Filter

Multilevel inverters that provide more than two levels of voltage to achieve less distorted dc-ac conversion have attracted many contributors. This paper presents a new simplied topology for single-phase, sinusoidal pulse width modulated (SPWM) three-level SPWM voltage source inverter (VSI) with LC filter. To keep the power circuit component count to a minimum, the proposed three-level topology simplies the conventional three-level inverter conguration to that of a full-bridge, two-level inverter, with only one added auxiliary power switch. Operational principles, with switching functions are analyzed. The performance characteristics of the proposed inverter are predicted using simulation process in simplorer schematic environment. Assessment of the proposed inverter is done by comparing it with the conventional single-phase, two and three level SPWM inverter under the conditions of identical supply dc voltage, switching frequencyand loading

Utility Interfaced Pulse-Width Modulation of Solar Fed Voltage Source Inverter Using Fixed-Band Hysteresis Current Controller Method

This paper describes a utility interfaced pulse-width modulation of solar-fed voltage source single phase full bridge inverter. The proposed system has to do with the conversion of solar energy into electrical energy; boosting the dc power; inversion of the dc to ac and then synchronization of the inverter output with the utility, and consequently, reduction of the total harmonics distortions in the supply. The proposed system will ensure steady state availability and suffciency of power supply to its areas of applications. To achieve this, current sensor, xed-band hysteresis current controller and lter were employed to ensure proper injection of power to utility side and vice versa. The computer simulations and spectral analysis of the system obtained from Simplorer Software were presented. This proposed system is designed for use in residential houses and industries

Space Vector Pulse Width Modulation of a Multi-Level Diode Clamped Converter with Experimental Verification

This paper presents the analysis of a multi-level diode clamped converter (DCC) which is implemented using space-vector pulse width modulation (SVPWM) technique, widely considered as the most efficient and easily applied modulation technique in most industrial drives and control applications. It also focuses on the step by step development of MATLAB /SIMULINK modeling of the space vector pulse-width modulation and the spectral analysis of the resultant waveforms obtained from the modulation results were carried out.  Results of the simulations obtained from DCC using SVPWM were equally presented and analyzed. This paper used generic on-time application method to realize the application time for the zero vector and two adjacent active vectors in determining the switching process of the multilevel DCC, quite unlike the look-up table which is common in this area. To verify the analysis, a small scale experimental work, was carried out. All experimental works were done in the laboratory and the results confirm the simulation results obtained from the SIMPLORER Student version 6 Software used in simulating the un-modulated three-level diode clamped converter

BACTERIOLOGICAL EVALUATION OF KWATA ABATTOIR WASTE WATER AWKA, NIGERIA

Abattoir wastes can have a detrimental effect on the environment, public health, animal health, and economy of a country if they are not effectively managed and controlled. The bacteriological evaluation of waste water from Kwata abattoir was carried out to determine the bacterial load present and if the waste water generated is suitable for direct discharge into the environment. A total of two samples were aseptically collected, in which the physicochemical analysis of the waste water showed objectionable color and odor, pH of 7.3 and 6.5, and temperature of 30.2°C and 25.3°C for samples A and B, respectively, of which the pH and temperature were within acceptable limits by WHO. The membrane filter method was used to determine the total coliform and thermotolerant coliform counts present per 100 mL of the samples using MacConkey agar and Eosin Methylene Blue Agar, respectively. The total viable count was obtained for both samples: 5.1×105 CFU/mL for sample A and 1.4×106 CFU/mL for sample B. Phenotypic and biochemical tests were carried out for four isolates, which include Escherichia coli, Salmonella spp., Bacillus spp., and Bacillus cereus. Thus, it can be concluded from the above study that untreated abattoir waste water contains a high level of pollutants, which supports the growth of the microbial population, as evidenced in the microbial study. Therefore, waste water has to be treated before discharge into the environment to protect public health and promote the safety of the environment