A general approach to synthesis and analysis of quasi-resonant converters

A method for systematic synthesis of quasi-resonant (QR) topologies by addition of resonant elements to a parent pulse-width modulation (PWM) converter network is proposed. It is found that there are six QR classes with two resonant elements, including two novel classes. More complex QR converters can be generated by a recursive application of the synthesis method. Topological definitions of all known and novel QR classes follow directly from the synthesis method and topological properties of PWM parents. The synthesis of QR converters is augmented by a study of possible switch realizations and operating modes. In particular, it is demonstrated that a controllable rectifier can be used to accomplish the constant-frequency control in all QR classes. Links between the QR converters and the underlying PWM networks are extended to general DC and small-signal AC models in which the model of the PWM parent is explicitly exposed. Results of steady-state analyses of selected QR classes and operating modes include boundaries of operating regions, DC characteristics, a comparison of switching transitions and switch stresses, and a discussion of relevant design trade-offs

The Alternate Arm Converter: A New Hybrid Multilevel Converter With DC-Fault Blocking Capability

This paper explains the working principles, supported by simulation results, of a new converter topology intended for HVDC applications, called the alternate arm converter (AAC). It is a hybrid between the modular multilevel converter, because of the presence of H-bridge cells, and the two-level converter, in the form of director switches in each arm. This converter is able to generate a multilevel ac voltage and since its stacks of cells consist of H-bridge cells instead of half-bridge cells, they are able to generate higher ac voltage than the dc terminal voltage. This allows the AAC to operate at an optimal point, called the “sweet spot,” where the ac and dc energy flows equal. The director switches in the AAC are responsible for alternating the conduction period of each arm, leading to a significant reduction in the number of cells in the stacks. Furthermore, the AAC can keep control of the current in the phase reactor even in case of a dc-side fault and support the ac grid, through a STATCOM mode. Simulation results and loss calculations are presented in this paper in order to support the claimed features of the AAC

Switching Flow-Graph nonlinear modeling technique

A unified graphical modeling technique, “Switching Flow-Graph” is developed to study the nonlinear dynamic behavior of pulse-width-modulated (PWM) switching converters. Switching converters are variable structure systems with linear subsystems. Each subsystem can be represented by a flow-graph. The Switching Flow-Graph is obtained by combining the flowgraphs of the subsystems through the use of switching branches. The Switching Flow-Graph model is easy to derive, and it provides a visual representation of a switching converter system. Experiments demonstrate that the Switching Flow-Graph model has very good accuracy

Supercapacitor assisted low dropout regulators (SCALDO) with reduced switches: A new approach to high efficiency VRM designs

Supercapacitor assisted low dropout (SCALDO) regulator is a new approach to develop high efficiency DC-DC converters with supercapacitors used for energy recovery. One limitation in these topologies is that in some configurations a large number of low-speed switches are required. If the SCALDO technique is adapted to build voltage regulator modules (VRM), it is necessary to reduce number of switches combined with a high current capable LDO. A new topology-variation with less number of switches can be achieved by reconfiguring the original SCALDO and adding an extra LDO to the circuit. The paper presents a summary of some preliminary work, and experimental results for a 2.5V proof of concept-prototype

Optimized power converters for electrically augmented on-orbit propulsion systems

Advances in satellite thruster technology have produced the requirement for high power electrical supplies to operate electrically augmented on-orbit propulsion systems. The power on board satellites is greatly limited by the solar panels that collect energy and the batteries that store the energy. In addition, satellites are constantly using power to operated their mission equipment and handle the communication requirements; This thesis investigates the power systems of modern satellites and the addition of an on-orbit electrically augmented propulsion system. The research process involves determining the system specifications, the power available and the thruster requirements. After determining the requirements, the implementation of the electrically augmented on-orbit propulsion system is characterized in terms of efficiency and potential electromagnetic compatibility. Several circuits are evaluated with the aid of PSPICE circuit simulation software and the results of the evaluation criteria for each circuit are presented

Modeling and Control of High-Voltage Direct-Current Transmission Systems: From Theory to Practice and Back

The problem of modeling and control of multi-terminal high-voltage direct-current transmission systems is addressed in this paper, which contains five main contributions. First, to propose a unified, physically motivated, modeling framework - based on port-Hamiltonian representations - of the various network topologies used in this application. Second, to prove that the system can be globally asymptotically stabilized with a decentralized PI control, that exploits its passivity properties. Close connections between the proposed PI and the popular Akagi's PQ instantaneous power method are also established. Third, to reveal the transient performance limitations of the proposed controller that, interestingly, is shown to be intrinsic to PI passivity-based control. Fourth, motivated by the latter, an outer-loop that overcomes the aforementioned limitations is proposed. The performance limitation of the PI, and its drastic improvement using outer-loop controls, are verified via simulations on a three-terminals benchmark example. A final contribution is a novel formulation of the power flow equations for the centralized references calculation

Efficient and Robust Simulation, Modeling and Characterization of IC Power Delivery Circuits

As the Moore’s Law continues to drive IC technology, power delivery has become one of the most difficult design challenges. Two of the major components in power delivery are DC-DC converters and power distribution networks, both of which are time-consuming to simulate and characterize using traditional approaches. In this dissertation, we propose a complete set of solutions to efficiently analyze DC-DC converters and power distribution networks by finding a perfect balance between efficiency and accuracy. To tackle the problem, we first present a novel envelope following method based on a numerically robust time-delayed phase condition to track the envelopes of circuit states under a varying switching frequency. By adopting three fast simulation techniques, our proposed method achieves higher speedup without comprising the accuracy of the results. The robustness and efficiency of the proposed method are demonstrated using several DCDC converter and oscillator circuits modeled using the industrial standard BSIM4 transistor models. A significant runtime speedup of up to 30X with respect to the conventional transient analysis is achieved for several DC-DC converters with strong nonlinear switching characteristics. We then take another approach, average modeling, to enhance the efficiency of analyzing DC-DC converters. We proposed a multi-harmonic model that not only predicts the DC response but also captures the harmonics of arbitrary degrees. The proposed full-order model retains the inductor current as a state variable and accurately captures the circuit dynamics even in the transient state. Furthermore, by continuously monitoring state variables, our model seamlessly transitions between continuous conduction mode and discontinuous conduction mode. The proposed model, when tested with a system decoupling technique, obtains up to 10X runtime speedups over transistor-level simulations with a maximum output voltage error that never exceeds 4%. Based on the multi-harmonic averaged model, we further developed the small-signal model that provides a complete characterization of both DC averages and higher-order harmonic responses. The proposed model captures important high-frequency overshoots and undershoots of the converter response, which are otherwise unaccounted for by the existing techniques. In two converter examples, the proposed model corrects the misleading results of the existing models by providing the truthful characterization of the overall converter AC response and offers important guidance for converter design and closed-loop control. To address the problem of time-consuming simulation of power distribution networks, we present a partition-based iterative method by integrating block-Jacobi method with support graph method. The former enjoys the ease of parallelization, however, lacks a direct control of the numerical properties of the produced partitions. In contrast, the latter operates on the maximum spanning tree of the circuit graph, which is optimized for fast numerical convergence, but is bottlenecked by its difficulty of parallelization. In our proposed method, the circuit partitioning is guided by the maximum spanning tree of the underlying circuit graph, offering essential guidance for achieving fast convergence. The resulting block-Jacobi-like preconditioner maximizes the numerical benefit inherited from support graph theory while lending itself to straightforward parallelization as a partitionbased method. The experimental results on IBM power grid suite and synthetic power grid benchmarks show that our proposed method speeds up the DC simulation by up to 11.5X over a state-of-the-art direct solver