The study presents the problem of the influence of the Z ‐Source circuit output impedance on the small signal control transfer function of a voltage source inverter (VSI). The previously published inverter design algorithms did not take into account the output impedance of the DC/DC voltage step‐up converters. The presented considerations should estimate the necessity of taking into account the Z ‐Source output impedance when designing an efficient control system for a DC/AC voltage inverter. It will be shown that the influence of the Z ‐Source storing energy in the inductances can be notable for low damping resistances and that it introduces two additional resonant frequencies to the nominator and denominator of the VSI control transfer function that are very close to each other. The magnitude Bode plots of the control transfer function of a VSI with a Z ‐Source are presented. The breadboard verification is also included.

This article presents a new generalised discrete model of the power stage of single- and three-phase inverters including the calculations of the output filter parameters that provide an acceptable level of output voltage harmonics. The presented model can be used with the pole placement control methods such as the coefficient diagram method or the deadbeat one sampling ahead preview control. Discrete modelling of the power stage including properties of the PWM modulator makes an easy description of the chosen control law that can be directly implemented in the control software possible. The final simulation and the experimental verification of the poles placement methods in the voltage source inventer control confirm the usefulness of the presented model but some differences between the control theory and the inverter measurements are expected.

This article presents the complete design of a low power voltage source inverter (VSI) dedicated for a UPS system. The analysis of the rectangular PWM-AC voltage spectrum allows for a choice of the basic architecture of the inverter. Output filter parameters were calculated to reduce the maximum amplitude of the output VSI voltage harmonics for the steady-state inverter mode. The choice of the feedback loop type was based on a discussion of the inverter output impedance using a continuous model of the inverter. The parameters of the inner loop digital control for the discrete inverter model were calculated using the Coefficient Diagram Method. The influence of the step load was modelled. The time constant of the inverter closed loop system was selected to ensure sufficient system robustness. An outer feedback loop with a plug-in repetitive controller, simplified owing to the properties of the PID/CDM inner loop control, was introduced to eliminate the periodic disturbances generated by the non-linear rectifier load and the deadtime influence. The experimental verification of the design method is presented.

The pulse‐width modulation (PWM) scheme is an algorithm for inverter switch control. A two‐leg bridge and three‐level PWM are typical solutions in voltage source inverters in uninterruptible power supply systems. The three PWM schemes that are used in inverters are compared herein. Each scheme has different features, including the level of noise generated and interference in the different frequency ranges. The aim of this study is to analyse the characteristics and electromagnetic interference that is generated by an inverter using different PWM schemes.

The standard single‐phase three‐level voltage source inverter (VSI) for uninterruptible power supply systems consist of a pulse width modulation (PWM) modulator, an H‐bridge, and an output inductance/capacitance filter. The design of most control systems requires the inverter small‐signal model. Two approaches for the discrete modelling of the VSI can be considered. The first is based on solving the state space equations during the switching period, which yields a discrete model that depends on the single‐edge or double‐edge type of PWM model. The second approach is the based on the continuous model of the inverter, which is derived from measurements of the real inverter and its discretisation. Both models should regard the increase in the real value of the equivalent coil series resistance and changes in the filter coil inductance with the frequency and amplitude of the magnetising current. The design of the control system requires experimental estimation of the additional delays, which are outside of the models during the measurements and modelling. Both models are validated by comparing the closed‐loop systems with the simple instantaneous controllers in the experimental model.

A comparative evaluation of the different, very popular powder magnetic materials for a voltage source inverter output filter coil core is presented. The basic continuous model of the inverter is simply based on the output filter transfer function. This model is used in the majority of inverter control designs. That is why the change of inductance and the increase of the equivalent serial resistance that is caused by power losses in the core and any other parasitic parameters of the coil should be known in the operating point because they depend on the frequency and the amplitude of the magnetising current. The theoretical calculation of these parameters variability is very inaccurate because of the complex voltage waveform on the coil, so the direct measurements of the inverter control transfer function are presented in aim to enable the choice of the most useful magnetic material for the inverter design.