Juan C. Jimenez

Analog Emulation of a Reconfigurable Tap Changing Transformer

Accurate analog models of power system components are required in order to realize an analog computation engine for power systems. Analog computation is an area of continued interest and has certain advantages over traditional digital computation. Among the advantages are physically realizable solutions and significantly faster computation times. This paper focuses on the development of a tap changing transformer model designed for a previously proposed method of analog power flow computation. Prior research in this field has modeled generators, loads and transmission lines. The transformer model proposed here provides a more accurate depiction of the network and captures the switching behavior of tap changing transformers. The transformer is modeled in analog form and a controller for the tap changing was developed in digital form. The model is verified via software simulation.

Simulation of a DC-DC boost converter with measurement delays

Power electronic converters are an important feature of many systems such as renewable energy systems, dc distribution systems and shipboard systems. The operations of such systems are highly reliant on their embedded communication infrastructures. Communication delays in delivering converter measurements across a computer controlled network can affect the accuracy of these measurements as viewed by remote hosts. With the preceding as motivation, this paper presents the simulation of an information embedded boost converter which observes measurement errors that result from delays in delivering the measurements. The embedded information network will be represented two ways; by a logistic growth and an exponential model. Results will concentrate on the effect of delays on the overall analysis of the converter.

Analysis of measurement delay errors in a DC-DC Buck-Boost converter using stochastic differential equations

This paper presents the use of stochastic differential equations (SDEs) to account for effects of network traffic on the communication of measurement data from a DC-DC Buck-Boost converter to a remote control center. The work is motivated by the need to account for observability of system states when a converter or system of converters is remotely monitored through a communication network comprised of switched networks. This work builds upon literature on SDEs used as appropriate tools to quantify the effects of uncertainty reflected in switched networks alone.

Circuit model of a phase-shifting transformer for analog power flow emulation

This paper focuses on the development of a phase shifting transformer model designed to be utilized in analog simulation (emulation). Simulation of power systems is necessary for both operation and planning and depends on suitable models of the components in the system. Analog computation as a technology for the analysis of large scale power systems represents a viable alternative to traditional digital methods as it provides certain advantages, such as speed and parallelism. Prior research in this field has modeled generators, loads and transmission lines. The transformer model proposed here provides a more accurate depiction of the network and captures the behavior of phase shifting transformers. The transformer is modeled in analog form. The circuit model is constructed and verified via software simulation using Analog Behavioral Models (ABMs) in PSpice and compared with industrial grade numerical simulator for validation.

Nonlinear analysis of multi-converter power systems for microgrids

Multi-converter power systems play an important role in leveraging microgrids to achieve increased levels of autonomy in power system operation. Desired performance of converters associated with this type of power system architectures can be accomplished via a set of executive and distributed control strategies. However, the effectiveness of these control mechanisms is dependent on the communication network employed for information passing. Consequently, the operation of the converters as well as the power system as a whole relies on knowledge of the conditions under which the control methodologies will become obsolete. These conditions can be described by bounds for plant and network parameters such as loading level and network delay respectively. The focus of this work is the description of static and dynamic behavior of multi-converter power systems, the trajectories of which will be investigated through simulations during disturbances that will prompt the system to breach these bounds.

Effects of communication network and load parameters on information-embedded multi-converter shipboard power systems

Information-embedded multi-converter shipboard power systems are comprised of multiple independently operated converters that work together with electromechanical equipment. Their relations can produce a large variety of dynamic and static interactions that can lead to irregular behavior of a converter, a group of converters or the whole system. This inherent cross-regulation behavior may correspond to controller limit violations, which results in harmful operational situations during system disturbances. It is significant then to monitor the system during perturbations; their underlying dynamics exhibit trajectories that not only depend on their independent operation modes. Appropriate modeling is a key issue to power system analysis and warrants primary investigation. This paper addresses aspects of modeling and simulation of multi-converter based shipboard power systems with the inclusion of power electronic equipment dynamics and network control in the overall system model. The model behavior is evaluated with respect to changes in loading conditions and control parameters (local and network) and validated through simulation of a nonlinear observability formulation of the developed system model.

Analysis of reconfigurable tap changing transformer model through analog emulation

Emulation of power systems is a viable alternative to traditional digital methods as it provides certain advantages such as physically realizable solutions and faster computation times. Accurate analog models of power systems components are required in order to realize an analog computation engine for power systems. Prior research in this field has modeled generators, transmission lines and loads. Other components have significant influence on the power systems, such as tap changing transformers. Effects of tap changing transformers on voltage stability have been a continuing area of research. In this paper, a circuit model design to emulate the behavior of a tap changing transformer is validated. It is important to demonstrate how this reconfigurable analog model may be utilized in load flow studies. Such demonstration is presented by comparing steady-state emulation and simulation results for a test case in which a power system experiences slow gradual changes in load.

Reconfigurable Phase Shifting Transformer for Analog Computation

This paper focuses on the development of a phase shifting transformer model designed for a previously proposed method of analog power flow computation. Prior research in this field has modeled generators, loads and transmission lines. Accurate analog models of power system components are required in order to realize an analog computation engine for power systems. Analog computation is an area of continued interest and has certain advantages over traditional digital computation. Among the advantages are physically realizable solutions and significantly faster computation times. The transformer model proposed here provides a more accurate depiction of the network and captures the behavior of phase shifting transformers. The transformer is modeled in analog form. The model is constructed and verified via software simulation.

Observability of network-delayed multi-converter power systems

Power electronic converter systems have become a key feature of smart grid technologies due to the efforts to achieve increased levels of autonomy in power system operation. However, when devising control strategies for multi-converter power systems, nonlinearities-associated issues with these types of systems arise (e.g. bifurcations) and must be taken into account as even a slight variation of a system parameter could change the structure of the system. With the increasing need for remote control, investigation of converter system dynamics alone is insufficient. Remote control is achieved via a communication system that is used for information passing between sensors and controllers, which hence plays an important role on the overall performance of the power system. Therefore, a need arises for the study of the power system (plant) and the communication system (network) as a single entity as the performance of one is highly dependent on the other. The focus of this work is the development of a metric that will serve as an indicator of overall system status to the power system operator.

Variations of converter's control parameters and its effects on DC multi-converter power systems

Different dynamic and static relations are possible in multi-converter power systems where electromechanical and power electronic equipment interact with each other. Harmful operational situations due to control limit violations can rise during system disturbances. The development of control strategies, be it local or system-wide, are key issues to maintain desired behavior of the system. This work concentrates on the modeling and simulation of a DC multi-converter power system to analyze the effects of load and control parameter variations in the overall behavior of the system and provides insight to possible issues to be included in the development of appropriate control strategies.