The application of DC grids is gaining more attention in office applications. Especially since powering an office desk would not require a high power connection to the main AC grid but could be made sustainable using solar power and battery storage. This would result in fewer converters and further advanced grid utilization. In this paper, a sustainable desk power application is described that can be used for powering typical office appliances such as computers, lighting, and telephones. The desk will be powered by a solar panel and has a battery for energy storage. The applied DC grid includes droop control for power management and can either operate stand-alone or connected to other DC-desks to create a meshed-grid system. A dynamic DC nano-grid is made using multiple self-developed half-bridge circuit boards controlled by microcontrollers. This grid is monitored and controlled using a lightweight network protocol, allowing for online integration. Droop control is used to create dynamic power management, allowing automated control for power consumption and production. Digital control is used to regulate the power flow, and drive other applications, including batteries and solar panels. The practical demonstrative setup is a small-sized desktop with applications built into it, such as a lamp, wireless charging pad, and laptop charge point for devices up to 45W. User control is added in the form of an interactive remote wireless touch panel and power consumption is monitored and stored in the cloud. The paper includes a description of technical implementation as well as power consumption measurements.
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Droop control is used for power management in DC grids. Based on the level of the DC grid voltage, the amount of power regulated to or from the appliance is regulated such, that power management is possible. The Universal 4 Leg is a laboratory setup for studying the functionality of a grid manager for power management. It has four independent outputs that can be regulated with pulse width modulation to control the power flow between the DC grid and for example, a rechargeable battery, solar panel or any passive load like lighting or heating.
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A lab-based test setup was developed to simulate a novel droop rate controlled DC bus charging plaza installation in the Netherlands. The system consists of multiple bidirectional DC charging points, a PV array and a bidirectional grid connection. Currently the installed system employs linear droop control at the charge points and active grid connection. This lab setup allows for the testing of new control schemes, such as piecewise linear droop control, before implementing in the installed system. The simulations performed in this study investigate a variety of power flow scenarios and determine appropriate voltage and current setpoints and control mechanisms.
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In this charging plaze energy exchange will be done by a DC microgrid between PV, V2G electric cars and lighting. Control is done autonomous with Droop Rate Control.
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• DC grid structure • Control • Switching • Protection • Stability
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This report gives a summary of how the control is set up for the DC grid in the VAP_DC project.
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The Smart Current Limiter is a switching DC to DC converter that provides a digitally pre-set input current control for inrush limiting and power management. Being able to digitally adjust the current level in combination with external feedback can be used for control systems like temperature control in high power DC appliances. Traditionally inrush current limiting is done using a passive resistance whose resistance changes depending on the current level. Bypassing this inrush limiting resister with a Mosfet improves efficiency and controllability, but footprint and losses remain large. A switched current mode controlled inrush limiter can limit inrush currents and even control the amount of current passing to the application. This enables power management and inrush current limitation in a single device. To reduce footprint and costs a balance between losses and cost-price on one side and electromagnetic interference on the other side is sought and an optimum switching frequency is chosen. To reduce cost and copper usage, switching happens on a high frequency of 300kHz. This increases the switching losses but greatly reduces the inductor size and cost compared to switching supplies running on lower frequencies. Additional filter circuits like snubbers are necessary to keep the control signals and therefore the output current stable.
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Het samenwerkingsverband van a.s.r., Kropman, Hogeschool van Amsterdam en Venema E-mobility heeft een pilot DC Nanogrid ontworpen waarin de betrouwbaarheid en veiligheid gewaarborgd zijn. Speciale aandacht tijdens dit project is besteed aan zwerfstromen, kathodische bescherming en autonome aansturing van het living lab op het a.s.r. verzekeringen parkeerdek. Een autonome systeembalans wordt gevonden door een Droop Rate Control (DrC) regeling. In het actieve DC-net heeft ieder component in het systeem een “gedragscode”: een eenvoudige regelstrategie die bepaalt wat het apparaat doet bij welke netspanning uitgaande van een nominale spanning (opwek en verbruik zijn in balans een hogere spanning (er is meer opwekvermogen aanwezig) of een lagere spanning (er is opwekvermogen te kort). Venema E-mobility heeft in dit project drie DC/DC laders ontwikkeld die zelfstandig met een drooprate control gestuurd worden. Het living-lab is getest en gekoppeld aan het bij a.s.r. aanwezige duurzame PV-opweksysteem en is onderdeel geworden van het grotere laadsysteem in het parkeerdek inclusief energiemanagement en beheeromgeving in InsiteSuite. De onderzoeks- en testresultaten zijn omgezet in conceptrichtlijnen en actief ingebracht in de Nederlandse normalisatie werkgroepen (NEN TC 64 en TC 81).
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Contribution to the conference: International Conference on New Pathways for Community Energy and Storage, 6-7 June 2019ABSTRACTThe community renewable energy is often seen as the way to address the societal challenge of energy transition. Many scholars foresee a key role for community energy in accelerating of the energy transition from fossil to renewable energy sources. For example, some authors investigated the transformative role of community renewable energy in the energy transition process (Seyfang and Smith, 2007; Seyfang and Haxeltine 2012; Seyfang et al. 2013; Seyfang et al. 2014; Smith et al. 2017; Martiskainen, 2017; Ruggiero et al. 2018; Hasanov and Zuidema, 2018; de Boer et al. 2018). Recognising the importance of community energy many scholars studied different internal and external conditions that contribute or hinder the success of local renewable energy initiatives (Walker et al. 2007; Bomberg and McEwen, 2012; Seyfang et al. 2013; Wirth, 2014; Hasanov and Zuidema, 2018; Ruggiero et al. 2018). One of such conditions contributing to the success of community energy initiatives is the capacity to adopt and utilize new technologies, for example, in the area of energy storage, which would increase flexibility and resilience of the communal energy supply systems.However, as noted by Ruggiero et al. (2018), the scholarship remains unclear on “how a very diverse and relatively small sector such as community energy could scale up and promote a change in the dominant way of energy production”. What is then the real transformative power of local renewable energy initiatives and whether community energy can offer an alternative to the existing energy system? This paper aims to answer these questions by confronting the critical review of theory with the recent practice of community energy in the Netherlands to build and scale up independent and self-sustaining renewable energy supply structures on the local and national scale and drafting perspectives on the possible role of community energy in the new energy system.
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