Julio C. Rosas-Caro

Novel DC-DC Multilevel Boost Converter

This paper proposes a new DC-DC converter. The DC-DC multilevel boost converter, based on one inductor, one switch, 2N-1 diodes and 2N-1 capacitor, for N levels plus the reference (total N+1 levels), is a boost converter able to control and maintain the same voltage in all the Nx output levels, and able to control the input current. This converter is based on the multilevel converters principle, and it is proposed to be used as DC-link in applications where several controlled voltage levels are needed with self balancing and unidirectional current flow, such as photovoltaic (PV) or fuel cell generation systems with multilevel inverters. Used to feed a multilevel inverter, the proposed topology achieves a self voltage balancing; experimental results prove the principle of the proposition.

A Transformer-less High-Gain Boost Converter With Input Current Ripple Cancelation at a Selectable Duty Cycle

This letter proposes a boost dc-dc converter topology with the novel capability of canceling the input current ripple at an arbitrarily preselected duty cycle. This is accomplished without increasing the count of the number of components in contrast to other solutions available in the literature. In addition, the converter features a high voltage gain without utilizing extreme values of duty cycle or boosting transformers. These features make the converter ideal to process electric power coming from low-voltage power-generating sources, such as renewables. This paper provides details on the principle of operation via topological considerations and a mathematical model. The key factor of reactive component sizing is also discussed in detail. The converter was validated in the laboratory through the construction of a hardware prototype.

Z-Source-Converter-Based Energy-Recycling Zero-Voltage Electronic Loads

This paper proposes two high-efficiency energy-recycling zero-voltage electronic loads (ELs) based on a Z-source converter. ELs are a family of power converters which are used as variable impedance loads in several applications. Such applications include testing of photovoltaic (PV) cells, power converters, and power supplies or frequency control of stand-alone microgeneration. In PV-cell performance tests, the zero-voltage operation, near the short-circuit point of the PV cells I- V curve, creates a challenge for EL design. The converter that is suitable for this application must have the ideal current source behavior because the challenge is to draw a specific constant current from the source under test even during the zero-voltage condition. The energy recycling principle increases the efficiency and allows the construction of high-power ELs. The proposed topologies are based on the Z-source converter and achieve the ideal current source behavior of draining an adjustable current even when the source voltage is zero. These topologies also provide power recycling for energy saving and for developing high-power ELs. The first configuration is based on the traditional Z-source converter, and the second one is based on the recently proposed quasi Z-source converter. Two prototypes were analyzed and built. Experimental results are provided to verify the principle of operation.

Modeling Approaches for DC–DC Converters With Switched Capacitors

In this paper, we review relevant problems in the modeling of dc-dc converters with switched capacitors. We study several approaches that overcome the exposed modeling difficulties, addressing ideal and nonideal cases and using dynamic equations that are valid in a large-signal domain.

A review of AC choppers

AC choppers are a family of ac-to-ac power converters that can be derived from the traditional dc-to-dc converters. Research activity in this kind of converter has recently increased in applications for power conditioning—such as voltage control in the distribution system and power flow control in the transmission system—as an alternative for the dc-link approach compensators based on voltage source converters. The control is simpler and the power rating of the devices is smaller for compensators with the same power rating; the main drawback is they cannot control the output-voltage frequency as the matrix converter. This paper presents a state-of-the-art review on the development of ac-choppers. The principle of operation is explained by using the six switches three-phase buck converter as an example. The main applications used in power conditioning and power flow control are introduced along with emerging topologies.

Z-source converter based zero voltage electronic load

This paper proposes a zero-voltage electronic load based on a Z-source converter. Electronic loads are a family of power converters used as a load in several applications such as photovoltaic [PV] cell performance tests or frequency control of stand alone micro generation. In PV cell performance tests; the zero voltage operation, caused by short circuit of the PV cell, is the main challenge for electronic load design. The ideal electronic load suitable for this application is an ideal current source because the challenge is to draw a specific constant current from the source under test [SUT] even during the zero voltage condition. The proposed converter which is based on the Z- source achieves the ideal current source behavior of draining an adjustable current even when the source voltage is zero. A prototype was built to verify the principle of operation and experimental results are provided.

Voltage balancing in DC/DC multilevel boost converters

This paper discusses the multilevel boost converter, a DC-DC converter recently proposed. The DC-DC multilevel boost converter is based on one inductor, one switch, 2N-1 diodes and 2N-1 capacitor, for an Nx converter, it is a boost converter able to control and maintain the same voltage in all the N output levels, and able to control the input current. The application proposed in this paper is the voltage balancing of the DC link in a diode clamped multilevel inverter, with the purpose to use it in renewable energy generation feed by a PV panel or by a fuel cell, where the DC input voltage needs to be boosted and regulated, a five level diode clamped multilevel inverter can be used to inject the power directly to the medium voltage distribution grid. The multilevel boost converter will balance the DC-link voltage; experimental results in a scaled low power prototype prove the propositions principle.

State space modeling and control of the dc-dc multilevel boost converter

The dc-dc multilevel boost converter topology was recently proposed with features such as high voltage gain without using an extreme duty ratio, few components and self dc-link balancing. This paper presents the state space modeling and a linear controller based on the pole placement technique for the dc-dc multilevel boost converter. Nonlinear and linear models are derived. Simulation results obtained with the averaging model in Matlab and with the simulated circuit in Synopsys Saber software are presented to prove the principle of the proposition.

Simple topologies for AC-link flexible AC transmission systems

Vector Switching Converter VeSC has been recently introduced as an alternative for controlling power flow in power systems complex interconnections by direct AC-AC conversion, and novel FACTS devices have been recently introduced based on the VeSC, such as the Xi (Ξ) and Gamma (Γ) controllers. This paper introduces the Simplified Vector Switching Converter SVeSC and the topology of the Xi (Ξ) and Gamma (Γ) controllers based on this novel simplified scheme, which reduce the number of switches, increasing the reliability and reducing the cost of implementation, while holds the operating principle. The control system of AC-link FACTS devices is simpler than the control system of the DC-link approach, and free of PLL and trigonometric calculations. Simulation results of the active power flow control between two nodes by the proposed simplified Xi (Ξ) controller are provided to prove the operating principle.

An Optimized Switching Strategy for a Ripple-Canceling Boost Converter

A hybrid switched-capacitor/interleaved boost converter able to provide a high voltage gain and to cancel the input current ripple at a preselected duty cycle was recently presented in the literature. This paper extends that work by proposing an optimized switching strategy for operating conditions at other values of duty cycle. The switching strategy effect on the converters voltage gain and input current ripple is quantified and compared against the performance under the conventional switching strategy. The approach is validated in the laboratory through hardware prototyping.