Husam A. Ramadan

Seamless dynamic model for bi-directional DC-DC converter

In this paper, bi-directional DC-DC converter is analyzed using a seamless dynamic model with an independent voltage source and an independent current source, which polarity depends on the direction of the power flow. In the seamless dynamic model, the independent voltage source represents a battery and an independent current source represents the load or energy source. A small signal model is derived using a state space averaging method, and simulated results about the transient response characteristics are presented.

A new stability assessment criterion for dc power systems using multi-level virtual conductors

This paper presents a new stability criterion for bidirectional DC-DC converters in a dc power system. Factually, it is so sophisticated to use conventional stability criteria to assess the stability of a dc power system consists of huge number of nodes. The proposed criterion gives an overall indicator for the stability at each node in the dc power system. It based on perturbing the system at a certain node by injecting a small ac current at this node, and accordingly monitoring the variation of the voltage at this node. Then, the node impedance can be calculated. This node impedance implies the stability status of the system at that node. The concept of the node impedance stability criterion is introduced, and the application of this criterion to a dc power system is investigated, as well.

A multi-level virtual conductor as a backbone of a DC power routing system

A new control approach for bidirectional DC-DC (BDC) converter is proposed in this paper. This approach aims at controlling a BDC in such a way that makes it behaves like a multi-level virtual conductor. As a matter of fact, the voltage difference between the terminals of any conductor is zero volts. Conversely, the main target of the proposed control approach is to keep the voltage difference between the converter terminals constant at certain value. In other words, the proposed control approach permits the DC-DC converter to transfer the power between two nodes at different voltage levels. In this way, the converter performs like a conductor but unlike the normal conductor, it has voltage deference between its terminals. Thus, the authors call it virtual conductor. This virtual conductor is considered a base to a power routing in dc networks; since it has the ability of transferring the electric power between nodes at different voltage levels. Furthermore, it allows an easy plug-and-play feature. The proposed BDC system configuration has been investigated analytically, using simulation, and experimentally.

Seamless dynamic model for DC-DC converters applicable to bi-directional power transfer

In this paper, seamless model of bi-directional DC-DC converter which is applicable to bi-directional power transfer is proposed. Conventional modeling method of bi-directional DC-DC converter is complex, because different models are needed for different directions of power flow. On the other hand, seamless model can be applied for both directions of power flow. Seamless circuit model is expressed by voltage source and bi-polar current source, and polarity of current source shows direction of power flow. In this model, control loop need to be switched by direction of power flow. Therefore analyzing and controlling bi-directional DC-DC converter is much easier than conventional way. Seamless dynamic model are derived by state-space averaging method. Analytical, simulated, experimental results are investigated, and availability of seamless model is suggested.

A unified model for The Multi-level Virtual Conductor

The Multi-level Virtual Conductor (MLVC) is a bidirectional DC-DC converter that has been controlled in a designated strategy so as to allow it to behave like a conductor has a voltage difference between its terminals. It is considered, in the MLVC, that both input and output of a bi-directional DC-DC converter are independent current sources. These current sources can be considered as a load or as power supply based on its polarity. Therefore, two control loops are required to stabilize the terminals voltages at a certain voltage difference in between. Accordingly, the controller design becomes a very complicated process. To facilitate this dilemma; one solution is to design the controller according to two stages. First stage: design the controller according to one loop control to stabilize one terminal voltage. While the second stage: design the controller according to one loop control to stabilize the other terminal voltage. Then design the controller of the MLVC based on the design considerations of the two cases. However this solution is an effective one and it begets good results. But, it is a heavy burden to perform the design procedure twice. Thus, this paper presents a unified model for the MLVC in order to ease the design procedures. This unified model helps to simplify the controller design process. The proposed unified model is investigated analytically and experimentally. Moreover, both of the frequency response and the transient response are analytically and experimentally studied, as well.