Matching Items (4)
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- All Subjects: Electric inverters
- Creators: Tsakalis, Konstantinos
Description
Traditional approaches to modeling microgrids include the behavior of each inverter operating in a particular network configuration and at a particular operating point. Such models quickly become computationally intensive for large systems. Similarly, traditional approaches to control do not use advanced methodologies and suffer from poor performance and limited operating range. In this document a linear model is derived for an inverter connected to the Thevenin equivalent of a microgrid. This model is then compared to a nonlinear simulation model and analyzed using the open and closed loop systems in both the time and frequency domains. The modeling error is quantified with emphasis on its use for controller design purposes. Control design examples are given using a Glover McFarlane controller, gain sched- uled Glover McFarlane controller, and bumpless transfer controller which are compared to the standard droop control approach. These examples serve as a guide to illustrate the use of multi-variable modeling techniques in the context of robust controller design and show that gain scheduled MIMO control techniques can extend the operating range of a microgrid. A hardware implementation is used to compare constant gain droop controllers with Glover McFarlane controllers and shows a clear advantage of the Glover McFarlane approach.
ContributorsSteenis, Joel (Author) / Ayyanar, Raja (Thesis advisor) / Mittelmann, Hans (Committee member) / Tsakalis, Konstantinos (Committee member) / Tylavsky, Daniel (Committee member) / Arizona State University (Publisher)
Created2013
Description
A new photovoltaic (PV) array power converter circuit is presented. The salient features of this inverter are: transformerless topology, grounded PV array, and only film capacitors. The motivations are to reduce cost, eliminate leakage ground currents, and improve reliability. The use of Silicon Carbide (SiC) transistors is the key enabling technology for this particular circuit to attain good efficiency.
Traditionally, grid connected PV inverters required a transformer for isolation and safety. The disadvantage of high frequency transformer based inverters is complexity and cost. Transformerless inverters have become more popular recently, although they can be challenging to implement because of possible high frequency currents through the PV array's stay capacitance to earth ground. Conventional PV inverters also typically utilize electrolytic capacitors for bulk power buffering. However such capacitors can be prone to decreased reliability.
The solution proposed here to solve these problems is a bi directional buck boost converter combined with half bridge inverters. This configuration enables grounding of the array's negative terminal and passive power decoupling with only film capacitors.
Several aspects of the proposed converter are discussed. First a literature review is presented on the issues to be addressed. The proposed circuit is then presented and examined in detail. This includes theory of operation, component selection, and control systems. An efficiency analysis is also conducted. Simulation results are then presented that show correct functionality. A hardware prototype is built and experiment results also prove the concept. Finally some further developments are mentioned.
As a summary of the research a new topology and control technique were developed. The resultant circuit is a high performance transformerless PV inverter with upwards of 97% efficiency.
Traditionally, grid connected PV inverters required a transformer for isolation and safety. The disadvantage of high frequency transformer based inverters is complexity and cost. Transformerless inverters have become more popular recently, although they can be challenging to implement because of possible high frequency currents through the PV array's stay capacitance to earth ground. Conventional PV inverters also typically utilize electrolytic capacitors for bulk power buffering. However such capacitors can be prone to decreased reliability.
The solution proposed here to solve these problems is a bi directional buck boost converter combined with half bridge inverters. This configuration enables grounding of the array's negative terminal and passive power decoupling with only film capacitors.
Several aspects of the proposed converter are discussed. First a literature review is presented on the issues to be addressed. The proposed circuit is then presented and examined in detail. This includes theory of operation, component selection, and control systems. An efficiency analysis is also conducted. Simulation results are then presented that show correct functionality. A hardware prototype is built and experiment results also prove the concept. Finally some further developments are mentioned.
As a summary of the research a new topology and control technique were developed. The resultant circuit is a high performance transformerless PV inverter with upwards of 97% efficiency.
ContributorsBreazeale, Lloyd C (Author) / Ayyanar, Raja (Thesis advisor) / Karady, George G. (Committee member) / Tylavsky, Daniel (Committee member) / Tsakalis, Konstantinos (Committee member) / Arizona State University (Publisher)
Created2014
Description
As the number of devices with wireless capabilities and the proximity of these devices to each other increases, better ways to handle the interference they cause need to be explored. Also important is for these devices to keep up with the demand for data rates while not compromising on industry established expectations of power consumption and mobility. Current methods of distributing the spectrum among all participants are expected to not cope with the demand in a very near future. In this thesis, the effect of employing sophisticated multiple-input, multiple-output (MIMO) systems in this regard is explored. The efficacy of systems which can make intelligent decisions on the transmission mode usage and power allocation to these modes becomes relevant in the current scenario, where the need for performance far exceeds the cost expendable on hardware. The effect of adding multiple antennas at either ends will be examined, the capacity of such systems and of networks comprised of many such participants will be evaluated. Methods of simulating said networks, and ways to achieve better performance by making intelligent transmission decisions will be proposed. Finally, a way of access control closer to the physical layer (a 'statistical MAC') and a possible metric to be used for such a MAC is suggested.
ContributorsThontadarya, Niranjan (Author) / Bliss, Daniel W (Thesis advisor) / Berisha, Visar (Committee member) / Ying, Lei (Committee member) / Arizona State University (Publisher)
Created2014
Description
This thesis addresses the design and control of three phase inverters. Such inverters are
used to produce three-phase sinusoidal voltages and currents from a DC source. They
are critical for injecting power from renewable energy sources into the grid. This is
especially true since many of these sources of energy are DC sources (e.g. solar
photovoltaic) or need to be stored in DC batteries because they are intermittent (e.g. wind
and solar). Two classes of inverters are examined in this thesis. A control-centric design
procedure is presented for each class. The first class of inverters is simple in that they
consist of three decoupled subsystems. Such inverters are characterized by no mutual
inductance between the three phases. As such, no multivariable coupling is present and
decentralized single-input single-output (SISO) control theory suffices to generate
acceptable control designs. For this class of inverters several families of controllers are
addressed in order to examine command following as well as input disturbance and noise
attenuation specifications. The goal here is to illuminate fundamental tradeoffs. Such
tradeoffs include an improvement in the in-band command following and output
disturbance attenuation versus a deterioration in out-of-band noise attenuation.
A fundamental deficiency associated with such inverters is their large size. This can be
remedied by designing a smaller core. This naturally leads to the second class of inverters
considered in this work. These inverters are characterized by significant mutual
inductances and multivariable coupling. As such, SISO control theory is generally not
adequate and multiple-input multiple-output (MIMO) theory becomes essential for
controlling these inverters.
used to produce three-phase sinusoidal voltages and currents from a DC source. They
are critical for injecting power from renewable energy sources into the grid. This is
especially true since many of these sources of energy are DC sources (e.g. solar
photovoltaic) or need to be stored in DC batteries because they are intermittent (e.g. wind
and solar). Two classes of inverters are examined in this thesis. A control-centric design
procedure is presented for each class. The first class of inverters is simple in that they
consist of three decoupled subsystems. Such inverters are characterized by no mutual
inductance between the three phases. As such, no multivariable coupling is present and
decentralized single-input single-output (SISO) control theory suffices to generate
acceptable control designs. For this class of inverters several families of controllers are
addressed in order to examine command following as well as input disturbance and noise
attenuation specifications. The goal here is to illuminate fundamental tradeoffs. Such
tradeoffs include an improvement in the in-band command following and output
disturbance attenuation versus a deterioration in out-of-band noise attenuation.
A fundamental deficiency associated with such inverters is their large size. This can be
remedied by designing a smaller core. This naturally leads to the second class of inverters
considered in this work. These inverters are characterized by significant mutual
inductances and multivariable coupling. As such, SISO control theory is generally not
adequate and multiple-input multiple-output (MIMO) theory becomes essential for
controlling these inverters.
ContributorsSarkar, Aratrik (Author) / Rodriguez, Armando A. (Thesis advisor) / Si, Jennie (Committee member) / Tsakalis, Konstantinos (Committee member) / Arizona State University (Publisher)
Created2015