Rene P. Torrico-Bascope

Highly Efficient High Step-Up Converter for Fuel-Cell Power Processing Based on Three-State Commutation Cell

The interest toward the application of fuel cells is increasing in the last years mainly due to the possibility of highly efficient decentralized clean energy generation. The output voltage of fuel-cell stacks is generally below 50 V. Consequently, low-power applications with high output voltage require a high gain for proper operation. Several solutions were so far proposed in the literature, ranging from the use of high-frequency transformers to capacitive multipliers. This paper proposes the modification of a boost converter operating with a three-state commutation cell that is already well suited for high current stress in the input due to the current sharing between the active switches. Here, an additional winding is added to the autotransformer to provide not only the required high gain but also to significantly reduce the voltage stress across the active switches. Moreover, by employing the three-state switching cell, the size of the inductor is reduced because the operating frequency is double of the switching frequency. A prototype for the verification of the circuit was built for a 30-45-V input-voltage range, 400-V output voltage, and 250-W output power. The operation is evaluated, and the experimental waveforms and efficiency curves are presented.

Novel Nonisolated High-Voltage Gain DC–DC Converters Based on 3SSC and VMC

This paper introduces a new family of dc-dc converters based on the three-state switching cell and voltage multiplier cells. A brief literature review is presented to demonstrate some advantages and inherent limitations of several topologies that are typically used in voltage step-up applications. In order to verify the operation principle of this family, the boost converter is chosen and investigated in detail. The behavior of the converter is analyzed through an extensive theoretical analysis, while its performance is investigated by experimental results obtained from a 1-kW laboratory prototype and relevant issues are discussed. The analyzed converter can be applied in uninterruptible power supplies, fuel cell systems, and is also adequate to operate as a high-gain boost stage with cascaded inverters in renewable energy systems. Furthermore, it is suitable in cases where dc voltage step-up is demanded, such as electrical fork-lift, audio amplifiers, and many other applications.

DC–DC Nonisolated Boost Converter Based on the Three-State Switching Cell and Voltage Multiplier Cells

This work introduces a dc-dc boost converter based on the three-state switching cell and voltage multiplier cells. A brief literature review is presented to demonstrate some advantages and inherent limitations of several topologies that are typically used in voltage step-up applications. The behavior of the converter is analyzed through an extensive theoretical analysis, while its performance is investigated by experimental results obtained from a 1-kW laboratory prototype, as relevant issues are discussed. The converter can be applied to uninterruptible power supplies and is also adequate to operate as a high gain boost stage cascaded with inverters in renewable energy systems. Furthermore, it can be applied to systems that demand dc voltage step up such as electrical fork-lift, renewable energy conversion systems, and many other applications.

A High Step-Up DC-DC Converter Based on Three-State Switching Cell

A new non-isolated boost converter with high voltage gain is proposed on this work. This converter is suitable for applications with a high voltage gain between the input and the output. In this converter, for a given duty cycle, the output to input voltage ratio can be raised by adding transformer turns. Another important feature of this converter is the lower blocking voltage across the controlled switches compared to similar circuits, which allows the utilization of MOSFETs switches with lower conduction resistances RDS(on). In order to verify the feasibility of this topology; principle of operation, theoretical analysis, and experimental waveforms are shown for a 1 kW assembled prototype

A UPS With 110-V/220-V Input Voltage and High-Frequency Transformer Isolation

This paper proposes an isolated double-conversion uninterruptible power system with power factor correction using a high-frequency transformer and with input voltages equal to 110 V/220 V. The arrangement is suitable to rack-type structures because it has a small size and a reduced weight. For both input voltages, the proposed converter has almost the same efficiency processing the same output power. Other relevant features include soft commutation of the controlled switches in the chopper and boost stages, a simple control strategy that can be implemented with well-known integrated circuits, and the use of few batteries in series due to the step-up stage. Qualitative analysis and experimental results obtained with a 2-kVA prototype show a normal efficiency of over 86% for the worst case of input voltage and an input power factor of over 99%.

A Generalized High Voltage Gain Boost Converter Based on Three-State Switching Cell

A new non-isolated step-up converter with high voltage gain is proposed on this work. It is suitable for applications with a high voltage gain between the input and the output. In this converter, the output to input voltage ratio, for a given duty cycle, can be raised adding transformer turns ratio. Another important feature of this converter is the lower blocking voltage across the controlled switches compared to similar circuits, which allows the utilization of switches with low on-resistance RDS(on) MOSFETs. In order to verify the feasibility of this topology; principle of operation, theoretical analysis, and experimental waveforms are shown for a 1 kW laboratory prototype

A Nonisolated DC-DC Boost Converter With High Voltage Gain and Balanced Output Voltage

This paper presents a dc-dc boost converter with high voltage gain based on the three-state switching cell for split-capacitor neutral-point-clamped inverters. The proposed converter is analyzed considering the operation in continuous conduction mode and duty cycle higher than 0.5, which corresponds to overlapping mode. The main characteristics of the topology are operation at high switching frequency, whereas the input inductor is designed for twice such frequency; in order to minimize weight and volume, the voltage stress across the switches is lower than half of the output voltage and naturally clamped by one output capacitor, allowing the use of MOSFET transistors with reduced intrinsic on-resistance; the input current presents small ripple; the output voltage can be further stepped up by increasing the transformer turns ratio without compromising the voltage stress across the switches; and the output voltage is naturally balanced, thus making the converter suitable for supplying split-capacitor inverters. Several topologies where a high voltage step-up is possible are initially investigated in the literature. Then, the principle of operation and experimental results for a 1-kW prototype are presented to validate the theoretical analysis and demonstrate the converter performance.

A Nonisolated Single-Phase UPS Topology With 110-V/220-V Input–Output Voltage Ratings

A circuit configuration of a single-phase nonisolated online uninterruptible power supply (UPS) with 110-V/220-V input–output voltage ratings is proposed, allowing the bypass operation without a transformer even if the input voltage is different from the output voltage. The converter consists of an ac–dc/dc–dc three-level boost converter combined with a double half-bridge inverter. In this type of configuration size, cost and efficiency are improved due to the reduced number of switches and batteries, and also, no low-frequency isolation transformer is required to realize bypass operation because of the common neutral connection. Both stages of the proposed circuit operate at high frequency by using a passive nondissipative snubber circuit in the boost converter and insulated-gate bipolar-transistor switches in the double half-bridge inverter, with low conduction losses, low tail current, and low switching losses. Principle of operation and experimental results for a 2.6-kVA prototype are presented to demonstrate the UPS performance.

A transformerless single phase on-line UPS with 110 V/220 V input output voltage

In this paper, it is proposed a new nonisolated UPS system configuration that allows the bypass circuit operation even if the input voltage is different from the output voltage. The UPS system is composed by an AC-DC/DC-DC three level boost rectifier/converter combined with a double half bridge inverter. This topology allows the reduction of some parameters that are commonly discussed in the nonisolated UPS systems such as size and cost, compared with others isolated UPS configurations for the same purpose. Also, the efficiency are improved due to reduced number of switches and batteries, as well as no low frequency isolation transformer is required to realize bypass operation because of the common neutral connection. Both stages of the proposed circuit operate in high frequency, using a passive nondissipative snubber circuit in the boost converter and IGBTs switches in the double half bridge inverter, with low conduction losses, low tail current and low switching losses. A simple and well-known control strategy is used. Principle of operation and experimental results for a 2.6 kVA laboratory prototype are presented to demonstrate UPS performance.

High frequency isolation on-line UPS system for low power applications

In this paper, a new high frequency isolation on-line uninterruptible power supply (UPS) system is proposed as a viable solution for low power applications. Its composed by one half-bridge chopper that operates in open loop with fixed duty cycle, a step-up converter that operates in closed loop using the traditional average current mode control and a traditional full bridge voltage source inverter (VSI). The step-up converter control provides power factor correction to the system. The proposed circuit is suitable for the development of low power UPSs (less than 1 kVA) which few batteries are used. In such applications the battery bank voltage, can be 24 V, 36 V or 48 V. Principle of operation, as well as, experimental results for the UPS operating in both, grid and battery modes are presented. Accordingly to the experimental results for a 1 kVA assembled prototype, an efficiency of 81,3% is obtained for grid mode and 89,2% for the battery mode, confirming the effectiveness of the proposed configuration.