Introducing Explicit Causality in Object-oriented Hybrid System Modeling

International audienceAlong with the rapid development of embedded devices and network technology, the area of CyberPhysical Systems (CPS), has arisen. In terms of modeling and simulation, CPS—like many technical systems—have ahybrid nature, i.e., discrete-event behavior and continuous-time dynamics have to be integrated with each other.Basically, this integration is supported by modern object-oriented modeling paradigms such as Modelica®. Theequation-based concept resolves the causality between interconnected components, which qualifies this modelingscheme for complex multi-domain systems. However, in hybrid systems, explicit causality is required to correctlymanage iterative events. This paper highlights these issues, including algorithmic loops and instantaneous multipleupdates, which essentially arise from incompatibilities between the object-oriented concept and specific discrete-eventphenomena. We discuss several possible solutions and introduce the concept of re-allocating the objects’ behavioralintelligence

Modeling and Simulation of a Wastewater Pumping Plant.

Modeling wastewater pumping plants is rarely addressed in the literature. Standard component models as found in fluid simulation tool libraries are too complex, due to their projected generality, to be used for these applications. Lack of models results in a burden on engineers who have to test their control scenarios on real implemented systems. This may lead to unexpected delays and painful costs. In this work, easily manageable component-oriented models are derived and applied to the modeling and simulation of a real wastewater pumping system. The model derived in this paper is implemented in Modelica, and it helps better understanding the system dynamics. Thereby, a tool is provided for evaluating the performance of possible control schemes

A framework for modeling and control of wastewater pumping stations

In waste water pumping stations, centrifugal pumps driven by induction motors are used to transport the effluent collected from residential and commercial buildings to the treatment plants. Due to the varying nature of collected effluent rate, means of pump flow control should be applied. Recently, there is an engineering debate on either recommending frequency converters control or on-and-off control using soft starter technology. While there are obvious reward and cost of utilizing either approach, the lack of a simulation model makes the selection decision a matter of poor agreement. This is likely to happen in developing areas where abnormal running conditions such as power failure, excess flows, and lack of spare parts are frequently encountered. In this paper, a method for modeling wastewater pumping stations using the component oriented modeling language Modelica is presented. The model provides a valuable simulation tool to validate and judge on the different control schemes of these stations. This approach is applied successfully on a real pumping station located at the northern part of Gaza. The derived model facilitates tuning the control parameters and allows better understanding of the system dynamics

Introducing Explicit Causality in Object-oriented Hybrid System Modeling

International audienceAlong with the rapid development of embedded devices and network technology, the area of CyberPhysical Systems (CPS), has arisen. In terms of modeling and simulation, CPS—like many technical systems—have ahybrid nature, i.e., discrete-event behavior and continuous-time dynamics have to be integrated with each other.Basically, this integration is supported by modern object-oriented modeling paradigms such as Modelica®. Theequation-based concept resolves the causality between interconnected components, which qualifies this modelingscheme for complex multi-domain systems. However, in hybrid systems, explicit causality is required to correctlymanage iterative events. This paper highlights these issues, including algorithmic loops and instantaneous multipleupdates, which essentially arise from incompatibilities between the object-oriented concept and specific discrete-eventphenomena. We discuss several possible solutions and introduce the concept of re-allocating the objects’ behavioralintelligence

Modeling wastewater pumping stations for cost-efficient control

In waste water pumping stations, centrifugal pumps driven by induction motors are used to transport the collected effluent to the treatment plants. Those pumps can be controlled either using frequency converters or on-and-off control using soft starters. In this paper a method for modeling wastewater pumping stations using the component oriented modeling language Modelica is presented. The model provides a valuable simulation tool to validate and judge on the different control schemes of these stations. This approach is applied successfully on a real pumping station located at the northern part of Gaza. The derived model facilitates tuning the control parameters and allows better understanding of the system dynamics

Modeling, Simulation and Control of a Water Recovery and Irrigation System.

For the modeling and simulation of large water recovery and irrigation systems, standard component models as found in simulation tool libraries are too complex. In this work, simple models are derived and applied for the modeling and simulation of a real system. In this system, water for irrigation will be collected by recovery wells around the wastewater treatment plant infiltration basins located in northern Gaza. There will be 27 recovery wells to collect the water in a reservoir before being distributed for irrigation via 10 booster pumps. During summer time, the system is expected to recover and distribute about 50885 m3 daily. The model derived in this paper using Modelica helps better understanding the system dynamics and provides a tool for evaluating the performance of possible control schemes

A Component-Oriented Model for Wastewater Pumping Plants

A typical wastewater pumping plant comprises a screening process and a pumping process. The first process separates coarse material out of wastewater, while the second one boosts the wastewater toward a treatment facility. Appropriate component models for such plants are hardly found in literature. Indeed, there exist standard component models in all-purpose fluid simulation tool libraries; their generality, however, makes those models too complex to be used for wastewater pumping plants. The lack of models forces engineers to test their control scenarios on real implemented systems, which may lead to unexpected delays and painful costs. In this work, easily manageable component-oriented models are derived and applied to the modeling and simulation of a real wastewater pumping system. The model derived here is implemented in the component-oriented Modelica language, and it helps better

Energy Management Scheme for Buildings Subject to Planned Grid Outages

A huge attention is paid to integrating buildings with renewable energy resources (RES) as a key factor to act on increasing demand. Meanwhile, utilizing different power resources can be a viable alternative for communities suffering from frequent and planned power outages. Conventionally, diesel generators are utilized as emergency backups to lessen the impact of power outages, but they consume a massive amount of fuel in case of extended outage periods. In this context, the work proposes an alternative microgrid power supply system incorporates photovoltaic solar array and lead-acid battery bank in addition to the conventionally utilized diesel generator for buildings experiencing frequent power outages. Besides, an energy management scheme is proposed to carry out the proposed supply. The main components of the system are modeled in MATLAB and the simulation is performed over a relatively long period (two weeks) to capture the pertinent dynamics of the system. The work is conducted using the example of Al-Shifa’ Hospital in Gaza-Strip to verify the effectiveness of the proposed approach. Moreover, different operation scenarios are tested from different perspectives with respect to the planned outages in Gaza-Strip. Simulation results indicate significant fuel savings in addition to a reduction in the total operation time of the diesel generator set (GenSet)