The high-voltage pulse generator is a crucial component for performing the electroporation process required in water treatment. This paper presents a three-state modulation for high-voltage pulse generator based on a modular converter structure. The converter consists of modular submodules connected in series, each comprising a half-bridge, a capacitor, and interconnecting diodes and inductors for series/parallel operation. The system eliminates the need for high-voltage switches and ensures a rapid dynamic response during the discharge process due to the absence of arm inductance. The proposal modulation allows to control the charging current, which is dependent on interconnecting inductors and switching frequency. The modulation technique is proposed, analyzed, and validated through simulation results.

This paper introduces a high-voltage pulse generator for water treatment, employing a multilevel modular converter structure. The pulse generator features completely modular submodules connected in series, each comprising a half-bridge, a capacitor, and interconnecting diodes for serial/parallel operation. It does not require high voltage switches and ensures a rapid dynamic response in output voltage because there is no arm inductance. The proposed converter provides flexibility, allowing configurable amplitudes and duration of the high voltage pulse. The power converter topology and a modulation technique are proposed, analyzed, and validated by simulation results.

The wireless power transfer technology for electric vehicles charging has been largely improved during the last years in terms of system configurations, coil design, and control schemes with the aim to achieve higher power, higher efficiency, and longer transmission distance. The compensation stage is usually designed considering sinusoidal voltages and currents. However, the full-bridge converters used to generate the controlled voltage generate a square waveform, requiring design adjustments, reducing the efficiency of the compensation, and impacting the control performance. In this paper, a design guideline for the compensation stage and the evaluation of the performance of the wireless power sources system using power converters instead of sinusoidal sources is given.

This work deals with the concepts to control a Multilevel Current-Source based Distribution Static Synchronous Compensator (MCSC-DSTATCOM) in order to reduce its steady-state losses. For this purpose, the analysis of the operating region is used to define a low-losses operating mode, leading to phase control of the power converter using a fixed modulation index. The mathematical analysis defines the proposal, which is corroborated using simulation in PSIM 9.0. Results show that it is possible to use the proposed control scheme, reducing the losses in the steady-state due to the use of the minimum dc current demanded by the equipment for required power compensation, also achieving high quality in the DSTATCOM at low switching frequency due to the use of the multilevel topology.

This work shows the use of the operating region of a D-STATCOM based on multilevel current-source inverters to define its operating point and its LC filter. A multilevel current-source D-STATCOM model is defined to compute its operating region and obtain a relation between reactive power compensation and the device power losses. Using this relationship the losses costs of the reactive power compensation is computed and used to define a methodology to get an operating point and design the LC as a function of the desired cost for nominal power compensation. The methodology is tested in the design of a 125kVA/380V distribution grid, where simulation results corroborate the analysis, including changes from one operating point to another, in open loop, to show the compensation capabilities, the power topology effort and the grid mains variables with compensation.

Power quality and reliability are inherent characteristics of the cascaded multilevel converters. However, in some converters, efforts should be made to ensure the durability and reliability of the equipment. This is the case of the single-phase current source cascaded inverter (SPCS-CI) in which, due to possible differences in the DC input current to each inverter of the system, it will be necessary to limit each output voltage of each unit. This can be done through a linear control strategy. In this work, the model and the mathematics of the problems caused by unbalanced DC currents in the described cascaded system are presented. Furthermore, a control scheme based on d-q reference frame components is proposed. Along with this, a control for the DC component voltages in the individual outputs of each inverter is added, which cannot be compensated completely by the d-q scheme. The proposed control strategy is a linear scheme with an updatable decoupler that allows to control d-q and DC voltages in a set of single-phase current source inverters disposed in a cascaded arrangement. Simulated results show the effectiveness of the proposed scheme.

Current source converters (CSC) are used in AC-Drives and Electrochemical applications requiring large and controlled currents. Usually, a controller/modulating block using pulse width modulation is employed to provide current control. Although, several works describing predictive controllers have been presented for both two-level and multilevel voltage source converters. Only a few report predictive control in CSC This paper proposes a predictive control strategy for CSC. The performance of proposed controller is compared with linear PI controllers in terms of speed, harmonic distortion and switching frequency. It is shown that the proposed strategy is suitable for Modular CSC. Theoretical analysis and simulation results that validate the proposed controlled are shown.

This work compares multi-cell topologies based on Current Source Inverters (CSIs) which are connected in a Cascade H-Bridge (CHB), where the large DC inductor size needed to compensate the oscillating power drained by the inverter is the main drawback. In order to reduce the DC inductor size, two compensation methods which compensated the oscillating power are evaluated and compared with the basic topology that use a large DC inductor. The first method consists in reducing the oscillating power through active compensation, which needs to supply the oscillating power from the rectifier, and the second method consists in reducing the oscillating power through magnetic coupling. The comparison considers the operating region, the DC inductor size, the magnetic power requirements, and the cell supply voltage requirements. Because the operating region is based on the converter and load parameters but independent of the DC inductor value, the passive parameters are designed as a function of the imposed rectifier input current quality and the load voltage THD. The comparison is done for a 9.33 MVA topology, simulating in PSEVI® in order to corroborate the components design and both the input current and load voltage quality. The operating region comparison is computed with one and two cells per phase and the achieved DC inductor reduction.

Nowadays the control of medium voltage motors has two main alternatives for its development: voltage source inverters (VSI); or current source inverters (CSI). The cascaded multilevel inverters derive from high voltage, high power quality and high reliability requirements in both development alternatives. Up to now, the cascaded multilevel converters have been implemented using voltage source power cells. However, they can also be implemented using current source units. One factor against CSIs is the large size of the inductive filters needed in the DC links, especially when single-phase inverters are considered. This paper presents a current-source cascaded multilevel converter (CS-CMC), based on single-phase power cells and their implementation alternatives, which enable a reduction in the sizes of the DC-link inductors. It is demonstrated that these sizes can be reduced using magnetic couplings between the DC links of the power cells. These magnetic couplings can eliminate second harmonic currents, as well as other even harmonics of current in the DC link of the power cells. This work asserts that the implementation of a current-source cascaded multilevel converter, based on single-phase power cells, must consider magnetic couplings between its DC links. Design results and the simulation of a development alternative of the system, aim to demonstrate the feasibility of implementing the cascaded multilevel converter.

Multilevel inverters are the alternative for medium voltage applications. Within the inverters types there are symmetric and asymmetric topologies. The asymmetric inverters have different DC voltage values. The most common topology is when the different cells are implemented in cascade arrangement, where the DC voltage are in multiples of 3, obtaining an AC voltage with 3n= 27 levels (n = 3 cascaded inverters). This topology provides a load voltage with low harmonic content, THD <; 3%. However, this high quality voltage has a non-negligible drawback, which is the presence of regeneration in some of the inverters, independent of load type. This phenomenon is due to the modulation technique (Nearest Level Modulation) used by this inverter. In this work, the asymmetric 15 level inverter is presented. This inverter is designed to avoid the regeneration problem - power flow from the load to the inverter - in some of the power cells. This is achieved by obtaining the firing angles associated with the power cells considering a minimum load voltage THD. Finally, a power flow analysis is accomplished and simulated results show the feasibility of this approach.

This work deals with the use of single-phase converters based on current-source inverters connected in a cascaded array (CSI-CHB) in order to get the dual topology of the classic Cascaded H-Bridged based on voltage-source inverters (CHB). The proposed configuration has similar advantages as the classic voltage source CHB as the use of semiconductors with lower voltage rating with respect to the load voltage. Moreover the CSI-CHB load voltage has a smaller distortion than the classic CHB due to the first order capacitive filter used at the inverters AC side. Also, the use of modulation techniques as phased-shifted carrier sinusoidal pulse modulation (PSC-SPWM) allows both, reduce the capacitive filter size and reduce the commutation frequency of the inverter switches. A theoretical analysis of the proposed topology and design guidelines for the capacitive filter are presented, considering a desired Total Harmonic Distortion (THD) on the load voltage and the SPWM modulation technique. Simulation results confirm the topology features.

A switching losses analysis is performed for an asymmetric multilevel Shunt Active Power Filter aimed to simultaneously compensate linear and nonlinear currents. The asymmetric approach consists in the inclusion of two types of modules; one meant for reactive power compensation and the other to cancel out the harmonic currents. Using the non-ideal behavior of the switching process in the power valves, the commutation losses of the presented approach are determined. Moreover, a comparison is performed with the symmetric counterpart and a power losses evaluation is made for both approaches. The analyses are carried out for a single operating point and for the entire operating region, considering the distorted power coming from the load. The presented results are supported with theoretical considerations and simulated waveforms.

Modular current source converters (MCSCs) have been proposed as an alternative method for increasing the power range of medium voltage PWM AC drives. MCSCs are built by stacking parallel current source converters. Two advantages that make MCSCs attractive are: (a) extended current/voltage ratings beyond the device ratings and (b) simplicity in balancing the DC link current in each module. This can be accomplished using two optimized modulating patterns that have been proposed for such topologies: (a) multilevel selective harmonic elimination (MSHE) and (b) displaced selective harmonic elimination (DSHE). Both techniques are based on SHE patterns but there are slight differences in their digital implementation due to the way they generate the harmonic cancellation. Furthermore, when these techniques are used in the rectifier stage, it is reported that MSHE and DSHE do not eliminate all the unwanted harmonics due to practical issues such as changes in the modulating indexes to control the DC link currents. This work compares the operation of DSHE and MSHE when used in rectifiers of an MCSC in terms of execution time, robustness to poor sampling frequency, and quality of harmonic profiles on AC input currents under different operating conditions. Experimental results are presented to validate the theoretical considerations.

The existence of single-phase inverters in cascaded multilevel AC/DC/AC converters implies the use of large capacitors in the DC links, because the H-bridge inverters demand considerable second harmonic currents that must be filtered out by the DC stage. If the filtering out is not strictly performed, the AC input current of each module is affected with the appearance of non-characteristic harmonics, sub-harmonics or inter-harmonics; thus, the RMS currents in the multi-pulse transformer secondaries increases. This problem may become even more evident if the converter output frequency is lower than the AC mains frequency, because the capacitor presents higher impedance at low frequency, causing that part of the harmonic currents demanded by the inverter is supplied directly by the rectifier. This paper presents an alternative to eliminate the unexpected harmonics and thus reduce the RMS values of the power cells input current in cascaded multilevel converters. The proposed solution uses magnetic couplings between the power modules of the converter; such approach is presented as a low cost solution compared to the conventional oversized DC-link capacitors.

Rectifiers delivering large DC currents (>1000 Ampere) at low voltages ( < 24 V) have significant conductive losses. Using controlled rectifiers to provide an output current following a reference increase those losses. An approach proposed in several works uses multi stage converters connected in cascade, where an AC/AC frequency changer is connected to an AC/DC diode based converter across a high frequency magnetic link. The AC/AC converter connected to the ac mains voltage boosts the frequency and provides control on the current delivered to the load. The DC converter delivers the output current at the load voltage. The main goal of these approaches is the reduction of conductive losses by performing the control on the AC/AC converter. Additionally, approaches using modular topologies offer additional advantages, especially in terms of reliability. This work presents a modular topology based on voltage source DC links. The topology is explained and simulations are presented in order to validate theoretical considerations.

A comprehensive solution to simultaneously compensate both reactive power and currents harmonics is presented for a multilevel STATic COMpensator (STATCOM). The proposed approach includes asymmetric power cells that independently compensate reactive power at fundamental frequency and cancel out the current harmonics coming from a nonlinear load. The presented analysis demonstrates that, under certain conditions, the modules aimed for harmonic cancellation require lower power than the modules that compensate the fundamental power factor. Thus, each module can be implemented with specialized power valves in order to improve the overall system performance. Simulated preliminary results confirm the correctness of the proposed approach.