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.

This paper presents a passivity-based control (PBC) design methodology for three-phase voltage source inverters (VSI) for uninterruptable power supply (UPS) systems where reduced harmonic distortions for the nonlinear load, reduced output voltage overshoot, and a restricted settling time are required. The output filter design and modification for efficient control and existing challenges with the assignment of scaling coefficients of the output voltage, load, and inductor currents are addressed and analyzed. Notably, special attention is given to the modulator saturation issue through implementing an accurate converter model. Applications of the two versions of PBC in three-phase voltage source inverters using stationary αβ and rotating dq frames for a constant frequency of the output voltage are presented. Furthermore, the influence of the PBC parameters on the power converter performance is investigated. A comparative simulation and the experimental results validate the effectiveness of the presented passivity-based control design methodology.

Single input single output systems (SISO), which only control the output voltage of a voltage source inverter (VSI) using multi-loop feedback, are not sufficient in the event of a 3-phase unbalanced load. A much better solution is a Multi Input Single Output (MISO) control. In such a case, not only is the output voltage controlled but also the output current and the output filter inductor current. It seems that using a Passivity Based Control (PBC) is just one of the better solutions for a VSI. The paper presents simulations of a modified Improved PBC (IPBC2) using a stationary αβ frame in the event of an unbalanced load in a 3-wire delta load. The simulations were verified using the measurements of a 3-phase inverter experimental model with dynamic balanced and unbalanced loads. DOI: http://dx.doi.org/10.5755/j01.eie.24.4.21474

This article presents the possibility of decreasing the inverter output voltage distortions that are caused by the typical distortions in the output voltage pulses of an impedance network using the qZ-source as an example. DC sources, such as photovoltaic cells with the qZ-source, increase the dc voltage; an impedance network operates in the continuous current mode and the discontinuous current mode (DCM). Both of these, but particularly DCM, implement the characteristic distortions to the impedance network output pulses, which results in the distortions in the inverter output voltage. It is possible to decrease these distortions in a passive way (increasing the capacitors of the network) or by using an efficient instantaneous controller of the inverter output voltage. Two controllers-a single-input single-output PID controller and a multi-input single-output improved passivity-based controller-were compared using the experimental model voltage source inverter with the input qZ-source.

Magnetic materials made of iron-powder that are used for the cores of the chokes of voltage source inverters output filters significantly change their power losses and magnetic properties with the frequency and the amplitude of the choke current in the range that is important for designers. This causes the magnitude Bode plot of the VSI control transfer function to have a higher damping coefficient and the resonant frequency that differs from the theoretically calculated one. The paper shows the influence of the properties of magnetic materials on the control of a voltage source inverter. The design of the control loop that takes into account the changes in these properties is presented and tested in the experimental model.

In modern controller design, various solutions for controlling power converter systems can be found depending on their applications, speed of working, pulse width modulation (PWM) techniques, switching frequencies—$f_c$, and different load types. The need to manipulate control parameters can be often observed in classical structures, e.g., well-known PID, repetitive, or deadbeat control particularly sensitive to distinct parameters uncertainties. The purpose of this paper is to present an improved version of controllers designated for a UPS that will be considerably resistant to model changes. Proposed control techniques are independent of unexpected output filter changes: $L_f$—filter coil inductance and $C_f$—filter capacitor conductance. The second aspect of this paper is to compare effectiveness of modified predictive MPC (model-predictive control) and feedback PBC (passivity-based control) controllers in reducing output voltage total harmonic distortion (THD) for various load values. The biggest distortions of output voltage were observed during experiments with nonlinear RC load. Both simulation and experimental verification of mismatching parameters were performed and examined. Thanks to the proposed solution, the output voltage $TH{D}_v$ quality factor was reduced below 8% in an efficient way for all the applied loads and stayed at the level of 1% when well-matched filter parameters were provided.