title: A supercapacitor assisted technique for reducing losses in the input loop of an inverter system for solar PV applications

authors: Naligama, Chamila Anuradha

subjects: switching converters

abstract: This paper presents a method of using supercapacitor modules in the input loop, to reduce the input losses of a typical inverter system used in solar applications. It is an extension of the supercapacitor-assisted loss management principle (SCALoM), where supercapacitors act as lossless droppers and energy buffers at the input end with a very low frequency switching scheme with reduced dynamic losses in switches compared to switched capacitor-inverter systems. The technique uses a set of micro-inverters, with the same total power capability as a single inverter, combined with a set of supercapacitor banks switching at a low frequency to reduce the voltage stress and rms current through the H-bridge input stages of the inverters, enhancing the end-to-end efficiency of the overall system. The proposed technique does not require a re-design of the commercially available inverters and adds DC-UPS capability to the system. Preliminary experimental results of the SCA(super capacitor assisted) two-inverter arrangement show stable transient and steady state operations, and the system is up to 2.2% efficient compared to a single central inverter arrangement. With the proposed SCA four-inverter configuration, inverter's overall power load can be further partitioned, and according to the analytical study further improvements in the overall efficiency can be achieved over the SCA two-inverter arrangement.

text: A supercapacitor assisted technique for reducing losses in the input loop of an inverter system for solar PV applications This paper presents a method of using supercapacitor modules in the input loop, to reduce the input losses of a typical inverter system used in solar applications. It is an extension of the supercapacitor-assisted loss management principle (SCALoM), where supercapacitors act as lossless droppers and energy buffers at the input end with a very low frequency switching scheme with reduced dynamic losses in switches compared to switched capacitor-inverter systems. The technique uses a set of micro-inverters, with the same total power capability as a single inverter, combined with a set of supercapacitor banks switching at a low frequency to reduce the voltage stress and rms current through the H-bridge input stages of the inverters, enhancing the end-to-end efficiency of the overall system. The proposed technique does not require a re-design of the commercially available inverters and adds DC-UPS capability to the system. Preliminary experimental results of the SCA(super capacitor assisted) two-inverter arrangement show stable transient and steady state operations, and the system is up to 2.2% efficient compared to a single central inverter arrangement. With the proposed SCA four-inverter configuration, inverter's overall power load can be further partitioned, and according to the analytical study further improvements in the overall efficiency can be achieved over the SCA two-inverter arrangement.

year: 2024

title: Compositional synthesis of supervisors in the form of state machines and state maps

authors: Mohajerani, Sahar

subjects: computer science

abstract: This paper investigates the compositional abstraction-based synthesis of least restrictive, controllable, and nonblocking supervisors for discrete event systems that are given as a large number of finite-state machines. It compares a previous algorithm that synthesises modular supervisors in the form of state machines, with an alternative that records state maps after each abstraction step and uses these to control the system. The state map-based algorithm supports all abstraction methods used previously, and in addition allows for nondeterminism, hiding, and transition removal. It has been implemented in the software tool Supremica and applied to several large industrial models. The experimental results and the complexity analysis show that state maps can be computed efficiently and in many cases require less memory than state machine-based supervisors.

text: Compositional synthesis of supervisors in the form of state machines and state maps This paper investigates the compositional abstraction-based synthesis of least restrictive, controllable, and nonblocking supervisors for discrete event systems that are given as a large number of finite-state machines. It compares a previous algorithm that synthesises modular supervisors in the form of state machines, with an alternative that records state maps after each abstraction step and uses these to control the system. The state map-based algorithm supports all abstraction methods used previously, and in addition allows for nondeterminism, hiding, and transition removal. It has been implemented in the software tool Supremica and applied to several large industrial models. The experimental results and the complexity analysis show that state maps can be computed efficiently and in many cases require less memory than state machine-based supervisors.

year: 2017

title: Nobody knows me even though I’m always there: Why Māori men do exist - in all the wrong places

authors: Stanley, Paul

subjects: Maori

abstract: In the study of psychology, Māori men are often only seen as the perpetrators of the problems. There is very little focus on finding solutions for Māori men, with Māori men. In the top eight causes of death for Māori males aged 15 to 24 are car crashes, homicide, and suicide. With respect to car crashes, there is a close link between alcohol-related car crashes and suicide. As a nation, we should be concerned with all of the above issues, as each of them is preventable. Invariably, we fail see the deaths of these young men as warning signs of much wider issues about why they wanted to die, or why they felt the need to kill someone close to themselves. The argument tendered in this paper is that the same way in which Māori as a group have been researched, as being “the problem”, equally applies to the way in which Māori men have continued to be have been researched: Māori men are only ever portrayed as “the problem” and are never portrayed as part of a solution subjected to this process as well. The lyrics of a well known song by UB40, One in Ten, exemplify this notion of being unknown, even though Māori men do exist in Aotearoa.

text: Nobody knows me even though I’m always there: Why Māori men do exist - in all the wrong places In the study of psychology, Māori men are often only seen as the perpetrators of the problems. There is very little focus on finding solutions for Māori men, with Māori men. In the top eight causes of death for Māori males aged 15 to 24 are car crashes, homicide, and suicide. With respect to car crashes, there is a close link between alcohol-related car crashes and suicide. As a nation, we should be concerned with all of the above issues, as each of them is preventable. Invariably, we fail see the deaths of these young men as warning signs of much wider issues about why they wanted to die, or why they felt the need to kill someone close to themselves. The argument tendered in this paper is that the same way in which Māori as a group have been researched, as being “the problem”, equally applies to the way in which Māori men have continued to be have been researched: Māori men are only ever portrayed as “the problem” and are never portrayed as part of a solution subjected to this process as well. The lyrics of a well known song by UB40, One in Ten, exemplify this notion of being unknown, even though Māori men do exist in Aotearoa.

year: 2003