Osama Abdel-Rahman

Modeling and Control of Three-Port DC/DC Converter Interface for Satellite Applications

This paper presents the control strategy and power management for an integrated three-port converter, which interfaces one solar input port, one bidirectional battery port, and an isolated output port. Multimode operations and multiloop designs are vital for such multiport converters. However, control design is difficult for a multiport converter to achieve multifunctional power management because of various cross-coupled control loops. Since there are various modes of operation, it is challenging to define different modes and to further implement autonomous mode transition based on the energy state of the three power ports. A competitive method is used to realize smooth and seamless mode transition. Multiport converter has plenty of interacting control loops due to integrated power trains. It is difficult to design close-loop controls without proper decoupling method. A detailed approach is provided utilizing state-space averaging method to obtain the converter model under different modes of operation, and then a decoupling network is introduced to allow separate controller designs. Simulation and experimental results verify the converter control design and power management during various operational modes.

An Integrated Four-Port DC/DC Converter for Renewable Energy Applications

This paper proposes a novel converter topology that interfaces four power ports: two sources, one bidirectional storage port, and one isolated load port. The proposed four-port dc/dc converter is derived by simply adding two switches and two diodes to the traditional half-bridge topology. Zero-voltage switching is realized for all four main switches. Three of the four ports can be tightly regulated by adjusting their independent duty-cycle values, while the fourth port is left unregulated to maintain the power balance for the system. Circuit analysis and design considerations are presented; the dynamic modeling and close-loop design guidance are given as well. Experimental results verify the proposed topology and confirm its ability to achieve tight independent control over three power-processing paths. This topology promises significant savings in component count and losses for renewable energy power-harvesting systems.

Transient Response Improvement in DC-DC Converters Using Output Capacitor Current for Faster Transient Detection

Demanding high power applications, such as fast processors, and pulsed loads are requiring new levels of performance from DC/DC converters. The requirements of high slew rate of load current with minimal output voltage deviation along with high conversion efficiency, small size and low cost, are all contradicting requirements for the DC/DC converter design. Proposed is a new approach to significantly limit the voltage overshoot and undershoot during load transient and reduce the number of capacitors, without compromising on the efficiency, cost or size of the DC/DC converter. It allow to optimize the power stage efficiency for the DC operation with less concern of dynamic performance, while an additional switching circuit; that utilizes the output capacitor current to detect load transient; is activated during load step up to deliver the shortage charge to the output capacitor, and also to pull out the extra charge from the output capacitor during load step down. Therefore, lower voltage deviation is achieved during load transient. The principle of operation and experimental results are presented.

An integrated three-port inverter for stand-alone PV applications

This paper presents a novel concept of integrated three-port interface for stand-alone photovoltaic applications. The three-port topology interfaces one solar panel input port and one bi-directional battery port to an isolated output port which generates a rectified sinusoid voltage. Then an unfolding circuit can be adopted to generate an ac wave with very high efficiency because it is operated at very low frequency (50/60Hz). Therefore, this proposed structure uses only one switch-mode conversion stage to replace several independent converters and inverters in order to reduce component count and save the cost, making itself a valuable choice for low cost low power standalone PV system. The circuit operation and control architecture of the three-port interface are presented. It can achieve maximum power harvesting for the solar port, battery charge control for the battery port, while keeping a regulated rectified sinusoid output. The experiments of the three-port interface confirm the topology operation and its ability to achieve the multi-functional power management control.

Dynamic Analysis of Three-Port DC/DC Converter for Space Applications

This paper presents the control structure for a novel three-port converter topology. This topology has the advantage of low switch count, high power density, high efficiency, so it is a valuable choice for space applications. The three port converter for space application interfaces one solar panel input port, one bi-directional battery port and an isolated output port. Lithium-Ion battery charge control simulation is implemented. Maximum Power Point Tracking (MPPT) is adopted to maximize the solar energy input. Two of the three ports can be simultaneously regulated. However, the two control loops have interactions with each other due to the integrated power trains of the three ports. Therefore, implementing the closed loop control requires careful analysis of their dynamic behaviors. In this paper, the dynamic behavior of the converter during different operational modes is fully characterized and studied. Small signal models are derived based on state space equations, and experimental results verify the converter control structure.

Multi-channel three-port DC/DC converters as maximum power tracker, battery charger and bus regulator

This paper presents the design and analysis of a satellite platform power system, which utilizes several three-port converters to interface various independent solar panels, one battery to a regulated bus. The three-port converter features low component count and compact structure. The paralleled three-port converters can not only boost the power level, but also provide redundancy, which is important to such critical applications. The proposed output port “hybrid” current sharing (CS) method shows good transients while requiring no interchannel level CS bus, meanwhile, the proposed passive CS method is well suited to both the MPPT algorithm for the input port and the battery charge control for the battery port. The analysis and design of the system level control strategy, the CS methods for three different ports, the MPPT and battery charging algorithms are verified by simulation and experiments.

Analysis and design for paralleled three-port DC/DC converters with democratic current sharing control

This paper presents a current sharing (CS) control structure for three-port DC/DC converters. Unlike regular two-port converters, three-port converters necessitate that two of three ports to have CS control simultaneously so that the third port achieves CS by default. The parallel operation of three-port converters for space applications requires a reliable CS structure to provide uniform current distribution among the modules. Both output port CS and battery port CS are achieved by paralleling CS loop and voltage regulation loop together according to the democratically elected maximum current reference. Stability is the main challenge for three-port paralleled systems as the added CS loops should not interact with abundance of control loops. Decoupled network and bandwidth limitation assumption are applied to ensure minimum loop interactions. Small signal analysis is applied to assess CS performance and judge system stability. The proposed CS structure is tested and verified by an experimental prototype.

An integrated four-port converter for compact and efficient hybrid power systems

As interest in renewable energy systems with various sources continues to grow, there is a strong need for integrated power converters that are capable of interfacing and concurrently controlling several power terminals. Meanwhile, energy storage is required to compensate for the mismatch between the sourcing and loading power patterns over a regular operational cycle. Therefore, different operational scenarios and modes exist during a regular operational cycle. This necessitates an intelligent power management and a mature and advanced control strategy in order to boost energy harvesting, protect the battery and increase overall system functionality, reliability and efficiency. The proposed four-port converter interfaces one photovoltaic (PV) panel input port, one wind turbine input port, one bi-directional battery port and an isolated output port. It has the advantage of low switch count, high power density and high efficiency. Wind and PV Maximum Power Point Tracking (MPPT), battery charge algorithm and bus voltage regulation are efficiently managed by a mature control structure.

Inductor current sharing of current doubler rectifier in isolated DC-DC converters

Current sharing is an important issue in both isolated and non-isolated dc-dc converters. In the paper, average current sharing is modeled and analyzed for isolated dc-dc converters with current doubler rectifier. Important design guidelines and conclusions are provided based on the mathematical modeling and analysis. A modified current doubler rectification is presented to achieve balanced current sharing between two inductors of current doubler rectifier in the half bridge dc-dc converter. Experimental results are presented to verify the analysis and proposed topologies

Active resonant tank to achieve zero-voltage-switching for non-isolated DC-DC converters with synchronous rectifiers

A concept of active resonant tank (ART) is proposed for high frequency non-isolated DC-DC converters to achieve zero-voltage-switching (ZVS) of the main switch and eliminate reverse recovery and body diode conduction losses of the synchronous rectifier in order to improve conversion efficiency and reduce EMI noises. The concept is generalized for six basic non-isolated converters. A buck converter with the ART cell is analyzed in great detail, and a 100 W prototype is built to verify the concept. Experimental results agree with theoretical analysis and improvement in efficiency is achieved due to the reduced switching and reverse-recovery losses