Euzeli C. dos Santos

Modulation for Three-Phase Transformerless Z-Source Inverter to Reduce Leakage Currents in Photovoltaic Systems

In this paper, a modified Z-source inverter (ZSI) with specific modulation techniques is proposed to reduce leakage currents in three-phase transformerless photovoltaic (PV) systems. The new topology only requires an additional fast-recovery diode when compared with the original structure. On the other hand, the pulsewidth modulation technique is entirely modified in order to reduce the leakage currents through the conduction path. Simulation results for the three-phase transformerless PV system operating in two cases, i.e., connected to a grid and connected to a grounded RL load, are presented. Experimental results of leakage currents in three-phase ZSIs connected to a RL load are obtained to validate the theoretical and simulation models.

Pulsewidth Modulation Strategies

This article reviews the nonsinusoidal CPWM and SVPWM techniques and deals with the three possibilities of calculation of pulsewidths after the addition of a zero-sequence signal. A general algorithm is proposed and adapted for dealing with the control of the three-level NPC inverter and also the Z-source converter. Experimental results corroborate the proposed technique.

Application of single-phase to three-phase converter motor drive systems with IGBT dual module losses reduction

This paper aims to apply a universal filter configuration to supply a three-phase motor from the single-phase grid, in this case the motor must be supplied with the same frequency of grid. The initial hypothesis consider that is possible to minimize the converters losses through the variation of motor voltage phase and through selection of an appropriate transformer. To reduce the IGBT dual module losses means to reduce the operational cost of the system. The initial investment of this configuration is very attractive for treating of a converter that works in shunt, in other words, only a part of the load power flows through the converter. Analysis in steady state has been realized, as well. Experimental results are showed to demonstrate the theoretical studied.

Single-Phase to Three-Phase Drive System Using Two Parallel Single-Phase Rectifiers

This paper proposes a single-phase to three-phase drive system composed of two parallel single-phase rectifiers, a three-phase inverter, and an induction motor. The proposed topology permits to reduce the rectifier switch currents, the harmonic distortion at the input converter side, and presents improvements on the fault tolerance characteristics. Even with the increase in the number of switches, the total energy loss of the proposed system may be lower than that of a conventional one. The model of the system is derived, and it is shown that the reduction of circulating current is an important objective in the system design. A suitable control strategy, including the pulsewidth modulation technique (PWM), is developed. Experimental results are presented as well.

Single-Phase to Three-Phase Universal Active Power Filter

In this paper, a universal active power filter is proposed for harmonic and reactive power compensation in the single-phase to three-phase systems. The proposed configuration solves a typical problem found in remote (or rural) applications, where only a single-phase grid is available and there is a demand to supply three-phase loads. A suitable control strategy is presented to regulate the load voltage, the power factor, and to minimize the voltage and current harmonics simultaneously. Simulated and experimental results are also presented.

Reversible AC Drive Systems Based on Parallel AC–AC DC-Link Converters

In this paper, two reversible single-phase-to-three-phase ac drive systems are proposed. They are composed of an induction motor fed by two parallel single-phase-to-three-phase dc-link converters without isolation transformers. Suitable modeling and control strategy of the systems based on odq approach, including the unbalanced case, are developed. The proposed topologies permit reducing the harmonic distortion and presents fault tolerance characteristics. Even if the number of switches is increased, the total energy loss of the proposed systems can be lower than that of a conventional one. It is shown that the reduction of the circulating current is an important objective for the system design. A single-phase-to-three-phase dc-link converter generalization has been proposed as well. Simulated and experimental results are presented.

Six-Phase Machine Drive System With Reversible Parallel AC–DC–AC Converters

This paper proposes a reversible six-phase machine drive system. It is composed of two parallel three-phase to three-phase dc-link converters without isolation transformers. The proposed topology permits one to reduce the harmonic distortion in the input converter and decreases the power processed by converter switches. Furthermore, the proposed configuration can guarantee the feasibility of the system when high-power applications are considered. The model and the control strategy have been developed. The simulation and experimental results are presented.

AC-AC single-phase DC-link converter with four controlled switches

An unidirectional single-phase to single-phase component minimized dc-link converter is discussed in this paper. It is composed of one unidirectional rectifier and one bidirectional inverter, using only four controlled switches. Suitable modeling and control strategy of the system, including a synchronization method, are proposed. The synchronization method, associated with the PWM command, guarantees a sinusoidal input current with the same phase angle of the input converter voltage. In this approach, the output converter voltage is also in synchronization with the grid. Proposed method eliminates zero-crossing distortion caused by the use of diodes, as well. Additionally, the control strategy permits the converter to operate with same dc-link voltage value required for the conventional six-switch converter. Simulated and experimental results are presented.

Improved power conditioning system for grid integration of photovoltaic solar energy conversion systems

The increasing utilization of photovoltaic (PV) solar systems in distributed (or dispersed) generation systems imposes new requirements for the operation and management of the distribution grid, especially when high penetration levels are achieved. Under this scenario, the power electronics technology plays a vital role in managing an effective grid integration of the PV system, since it is subject to requirements related not only to the intermittent source itself but also to its effects on the grid operation. This paper proposes an improved structure of power conditioning system (PCS) for the grid integration of PV solar systems. The topology employed consists of a three-level cascaded Z-source inverter and allows the flexible, efficient and reliable generation of high quality electric power from the PV array. A full detailed model is described and its control scheme is designed. Validation of models and control schemes is carried out through digital simulations using the MATLAB/Simulink environment.

Advanced power conditioning system for grid integration of direct-driven PMSG wind turbines

The increasing use of distributed generation (DG), particularly based on wind power systems, requires new strategies for the operation and management of the power distribution system, especially with high installed capacity. Under this scenario, the power electronic technology plays an important role in the integration of DG into the electrical grid since the DG system is subject to requirements related not only to the renewable energy source itself but also to its effects on the power system operation. This paper proposes an improved structure of power conditioning system (PCS) for the effective grid integration of wind turbine generators (WTGs). The topology employed consists of a three-level Z-source cascaded inverter and allows the flexible, efficient and reliable generation of high quality electric power from the WTG system. A full detailed model is described and its control scheme is designed. Validation of models and control schemes is performed using the MATLAB/Simulink environment.