The increasing availability of digital computers now makes the computer-aided design of powerelectronic systems an attractive and cost-effective development tool. The paper describes the detailed development of an extremely versatile PWM computer modelling package which can be used as a `stand-alone′ package for harmonic analysis, or alternatively as a `building-block′ for developing more complex systems. The capabilities of the package are demonstrated, using a number of examples of single-phase and 3-phase PWM inverters, which serve to highlight a number of important operational characteristics of PWM inverters. The validity and accuracy of the computer simulations are confirmed, using experimental results obtained from a microprocessor-controlled PWM inverter-drive system.

Computer-Aided Design of PWM Inverter Systems

The invention relates to an inverter circuit having a primary circuit and a secondary circuit which are galvanically isolated by means of a transformer (T) with the primary circuit having means for clocked connection of a primary winding (NP) to a DC voltage (VIN) which is applied to the input of the inverter circuit, and with the secondary circuit having means for connection of a secondary winding (NS) to an AC voltage (VMAINS) which is produced at the output of the inverter circuit, with the primary circuit furthermore being connected by means of a first inductor (LP) to the DC voltage (VIN), and with the secondary winding (NS) being connected to the AC voltage (VMAINS) by means of a second inductor (LS) in series with a first capacitor (CS), via a full bridge which is formed from four switching elements (S1, S2, S3, S4).

Inverter circuit and method for operating the inverter circuit

A technique is presented for harmonic reduction in inverters using sinusoidal pulse-width modulation (PWM). A modified circuit based on parallel operation of MOS-based inverter sets using interphase reactors as harmonic reducing elements and making use of a specific phase shift between the modulating and carrier waveforms is investigated as a means to economically and efficiently reduce the harmonic contents in the output waveform. The output waveform of a single-phase PWM inverter is investigated both theoretically and experimentally. Detailed analysis shows that the harmonics lower than the 15th are all less than 1% of the fundamental component when the frequency ratio is relatively low, i.e. about nine and similarly for the 29th harmonic when the ratio is about 15. This is done without noticeable reduction in the fundamental component. The results show the feasibility of obtaining practically sinusoidal output waveforms. >

Harmonic reduction in single-phase inverter using a parallel operation technique

There is described a method for operating an electronically controlled inverter. The inverter is controlled during the positive half-wave of the output alternating voltage in such a way that it operates as a SEPIC converter, and during the negative half-wave of the output alternating voltage in such a way that it operates as a CUK converter.

Method for Operating an Inverter and Arrangement for Executing the Method

A technique for reducing the total harmonic distortion in the voltage output of naturally sampled pulse width modulated inverters is investigated. This technique is based on synchronization of parallel-connected inverters and makes use of a phase-shift in transistor gating between these inverters. Often, in practice parallel inverters are operated with no synchronization, resulting in far less than optimal harmonic distortion reduction. The output waveform of a single inverter, two parallel inverters, and three parallel inverters is analyzed and compared in simulation and experimentally. This is done for two and three level pulse width modulation, for several values of modulation index, and different carrier to fundamental frequency ratios. Both simulation and experimental results indicate that a significant reduction in total harmonic distortion occurs using the synchronization technique, and observations are provided on the ability to reduce harmonic distortion in multiple inverter systems.

Characterization of Distortion Reduction for Single-Phase Multiple Inverter Operation

Microprocessor control of power electronic systems offers the possibility of improvements in reliability, maintenance and servicing, and increased control flexibility. This paper describes several pulsewidth modulation (PWM) waveforms where a predetermined number of unwanted harmonics can be canceled. The advantages and disadvantages of the different methods of delaying the signals in small microprocessor controlled PWM inverter drive systems are considered. Several examples of single-phase and three-phase PWM inverters, with the laws which govern the commutation angles, output waveforms, and their respective frequency spectra are presented.

Microprocessor Control of DC/AC Static Converters

Computer Aided Generation of Microprocessor Software for Controlling Static Power Converters

Abstrac. This paper presents a microprocessor based control circuit using the MC6802, which generates all the control signals necessary for feeding AC motors.

Basis on the ″Control Rose Theory″ and the ″Existential Function Modulation″ (E.F.M.) method suitable algorithms, which cancel a number of predetermined unwanted harmonics, for an Unrestricted Frequency Changer and a three phase bridge inverter have been developed.

Using these theories as a working tool, control circuits, specially adapted to fed AC motors are herewith presented.

C.M. Peñalver

Papers

Microprocessor Control of DC/AC Static Converters

Computer Aided Generation of Microprocessor Software for Controlling Static Power Converters

An optimal microcomputer-controlled converter for feeding ac motors

An Optimal Microcomputer-Controlled Converter for Feeding AC Motors