Alessandro Luiz Batschauer

Three-Phase Hybrid Multilevel Inverter Based on Half-Bridge Modules

A novel three-phase hybrid multilevel converter is proposed for medium-voltage applications. The converter employs a conventional three-phase voltage source inverter (VSI) linking series connected half-bridge modules at each phase. With the proposed connection, a large portion of energy can be processed by the VSI by employing a single multi-pulse rectifier, while smaller power shares are processed within the half-bridge modules. Thus, the requirements for galvanically insulated dc sources are reduced. Modularity is naturally achieved. A modulation scheme for a four-level version is proposed and analyzed in detail. This scheme allows unidirectional power flow in all dc sources and, consequently, enables diode bridges to be employed in the rectification input stage for unidirectional applications.

Hybrid multilevel converter employing half-bridge modules

A novel hybrid three-phase multilevel converter is proposed for medium-voltage applications. The converter employs a conventional three-phase voltage source inverter (VSI) linking series connected half-bridge modules at each phase. With the proposed connection, a large portion of energy can be processed by the VSI without the need for insulation or by employing a single transformer, while smaller power shares are processed within the half-bridge modules. Thus, the requirements for galvan-ically insulated dc sources are reduced. Modularity is naturally achieved. A modulation scheme for a four-level version is proposed and analyzed in detail. This scheme allows unidirectional power flow in all dc sources and, consequently enables diode bridges to be employed in the rectification input stage for unidirectional applications.

Evaluation of the hybrid four-level converter employing half-bridge modules for two different modulation schemes

A novel hybrid three-phase multilevel converter is proposed for medium-voltage applications. The converter employs a conventional three-phase voltage source inverter (VSI) linking series connected half-bridge modules at each phase. With the proposed connection, a large portion of energy can be processed by the VSI without the need for insulation or by employing a single transformer, while smaller power shares are processed within the half-bridge modules. Thus, the requirements for galvanically insulated dc sources are reduced. Modularity is naturally achieved. A modulation scheme for a four-level version is proposed and analyzed in detail. This scheme allows unidirectional power flow in all dc sources and, consequently enables diode bridges to be employed in the rectification input stage for unidirectional applications.

A Voltage Regulator for Power Quality Improvement in Low-Voltage Distribution Grids

This paper presents a voltage-controlled distribution static synchronous compensator (DSTATCOM)-based voltage regulator for low-voltage distribution grids. The voltage regulator is designed to temporarily meet the grid code, postponing unplanned investments while a definitive solution could be planned to solve regulation issues. The power stage is composed of a three-phase four-wire voltage-source inverter and a second-order low-pass filter. The control strategy has three output voltage loops with active damping and two dc bus voltage loops. In addition, two loops are included to the proposed control strategy: the concept of minimum power point tracking (mPPT) and the frequency loop. The mPPT allows the voltage regulator to operate at the minimum power point, avoiding the circulation of unnecessary reactive compensation. The frequency loop allows the voltage regulator to be independent of the grid voltage information, especially the grid angle, using only the information available at the point-of-common coupling. Experimental results show the regulation capacity, the features of the mPPT algorithm for linear and nonlinear loads, and the frequency stability.

A voltage regulator based in a voltage-controlled DSTATCOM with minimum power point tracker

This paper presents a voltage regulator based in a Distribution Static Synchronous Compensator (DSTATCOM) applied to low voltage distribution grids. The DSTATCOM consists in a three-phase four-wire Voltage Source Inverter (VSI) connected to the grid through a second order low pass filter. The control structure is composed of three output voltage loops with active damping and the two dc bus loops. In addition, a new concept of Minimum Power Point Tracking (mPPT) is introduced, forcing the DSTATCOM to operate with the minimum power. In certain conditions, this means no compensation. The dynamic models of the converter are presented, as well as the control design. Simulation results show the capacity of regulation and the features of the mPPT.

Comparison between a hybrid multilevel converter employing half-bridge modules and a hybrid multilevel converter employing H-Bridge modules

The Hybrid Cascaded Half-Bridge (HC½B) converter is a multilevel circuit topology that is able to replace a Hybrid Cascaded H-Bridge (HCHB) converter regarding voltage vector generation, modularity and other features. However, there is not a complete correspondence between the converters since they present different operation principles. This work presents a comparison between the (HC½B) and the (HCHB). The converters are analyzed in their four-level versions, but the results are valid for other configurations. The comparison comprehends the power semiconductors, the generated voltages, the isolated dc supplies and the dc-link capacitors. It is shown that the main differences are with the dc link capacitors. Thus, these are analyzed in detail and a modeling procedure to design and compare them is proposed.

A DC-DC ZVS Phase-Shift PWM full-bridge current-mode controlled converter with multiples outputs for photovoltaic applications

This work proposes a new application of a DC-DC zero-voltage switching (ZVS) full-bridge converter in a photovoltaic (PV) energy system. On its input is connected a photovoltaic array, mostly parallel connected, resulting in a low voltage input. The control applied to the converter is a peak current-mode control, controlling its input current and performing the maximum power point (MPP) tracking (MPPT). The DC-DC converter provides three current outputs isolated by a high frequency transformer for a three-phase line-commutated 18-pulse inverter. Results of a 2.3kW converter simulation and preliminary experimental results are presented.

Frequency compensation for stand alone voltage-controlled DSTATCOM

This paper presents a simple control loop for voltage-controlled DSTATCOMs able to mitigate the effects of grid frequency deviation, greatly increasing the voltage regulation autonomy. The DSTATCOM consists of a three-phase four-wire Voltage Source Inverter (VSI) connected to the grid through a second order low pass filter. The control structure is composed of the conventional loops: three for the output voltage with active damping, and two for dc bus voltages, along to the frequency loop. The inclusion of the frequency loop makes the grid voltage phase information no longer needed. In other words, only the PCC voltage information is needed for the DSTATCOM operation. Experimental results prove its features and the effectiveness of the new loop.

Using MPPT in multi-pulse converters for photovoltaic cogeneration

One alternative for the processing of energy acquired by photovoltaic panels is the use of phase-controlled inverters associated with multi-pulse autotransformers, which is nothing more than a dual system for multi-pulse rectifiers. This converter has advantages related to robustness, low maintenance, reliability and low cost. Another important feature is that the use of transformers with specific displacement reduces the quantity of harmonic current injected into the grid. This paper will present this converter and proposes the use of Maximum Power Point Tracking (MPPT) acting on the average input voltage of the inverter, using the trigger angle to vary the average voltage of the converter and keep it operating at the maximum power point of the PV panels.

A simple control scheme to a voltage regulator based in a current controlled STATCOM

This work shows a simplified control scheme to a Static Synchronous Compensator (STATCOM) based regulator, used to regulate the voltage magnitude in AC low voltage grids. The system regulates the voltage through injection of reactive power at the point of common coupling (PCC). The regulator was implemented by a three-phase four-wire current-controlled voltage source converter (VSC), connected in shunt with the PCC. The reactive power processed by converter is responsible to regulate the PCC voltage while the active power is responsible for the control of the DC bus voltage. In this paper it is presented the control design and some experimental results of a 4.5kVA implemented prototype.