Introducing small storage capacity at residential PV installations to prevent overvoltages

Low voltage distribution feeders are designed for unidirectional energy supply from transformer to consumer. However, the implementation of small-scale PV production units on local utilities may result in bidirectional energy flows. The simultaneous power injection at sunny moments may cause a serious voltage rise along the feeder. These overvoltages may not only damage critical loads but also switches PV inverters off causing loss of green energy at the most productive moments. This paper presents a method to limit the voltage rise by introducing small battery buffers at local production sites. A smart inverter decides whether the PV energy is injected in the grid or buffered in the batteries. The relation between battery buffer size and overvoltage reduction is presented for a typical Belgian residential distribution feeder. The influence of the buffer along the feeder is calculated by working with synthetic load profiles and solar irradiation data

An energy efficient breakdown cover service for electric cars

A typical breakdown cover service unit in Belgium has to assist up to 5 cars a day that end up with an empty fuel tank. As the range of today’s battery electric cars is lower than what people are used to have today, breakdown cover services expect that massive introduction of electric cars will lead to a multiple of EVs ending up with an empty battery. This paper reports about a research project, initiated by a Belgian breakdown cover service, that aimed to design and build a prototype of a fast and an energy efficient intervention car for EVs with empty batteries. For the prototype a CNG van is equipped with a hybrid power system enabling efficient energy injections for electric vehicles with slow as well as fast charging possibilities. The prototype is equipped with charging infrastructure providing mode 1, 2 and 3 charging. The paper starts with a description of the prototype design. The main part gives a detailed comparison of three EV breakdown cover service methods: towing the EV, energy injection on the spot by a diesel genset on a diesel truck and energy injection with the designed prototype. For a typical breakdown cover service day, the prototype turns out to be 12% faster, consumes 41% less energy and reduces emissions by 68% in comparison with towing.status: publishe

Variable speed genset with full rated power converter using readily available industrial products

Although a classic diesel genset may reach 35% efficiency at nominal load, it has very poor efficiency at low load conditions. Still, these conditions often occur in real world applications when combining gensets with variable autonomous loads. Previously, the authors built a hybrid genset prototype achieving fuel consumption reductions of over 30%. As an alternative to this hybrid genset, this paper reports on a variable speed genset prototype. To demonstrate a higher fuel efficiency, a prototype 50 kVA variable speed genset has been built using readily available industrial products. A diesel internal combustion engine supplies power to a PM synchronous generator to produce variable voltage, variable frequency AC. Using a four-quadrant variable-frequency drive and transformer this electrical energy is converted to produce an autonomous 4-wire 50 Hz 3×400 V grid. Operation principle, prototype implementation, first load tests (speed response and power quality) and possible improvements are discussed in this paper.status: publishe

Testing Compliance of Wireless Power Transmitters to EMC and Public Health Legislation

Over the past years, the interest in wireless power transfer with resonant inductive coupling has grown in the consumer electronics industry. Since then, several appliances using this technology have been brought on the market. Most of them are meant for charging handheld devices. In general, a wireless power system consists of a transmitter and a receiver. These devices contain inductively coupled coils that typically resonate at frequencies in the range of tens to hundreds of kHz. Inherent to wireless power transmitters, electrical and magnetic fields are generated in the vicinity of the device. Because of the potential health hazards and electromagnetic interference that these fields may cause, they are subject to certain regulations. However, the regulations for ElectroMagnetic Compatibility (EMC) and the public health legislation are not clearly defined for these devices. This paper studies the currently applicable norms, recent evolutions and possible future normative work in the European Union.status: publishe

Home charging of electric vehicles in Belgium

status: publishe

Introducing small storage capacity at residential PV installations to prevent overvoltages

Low voltage distribution feeders are designed for unidirectional energy supply from transformer to consumer. However, the implementation of small-scale PV production units on local utilities may result in bidirectional energy flows. The simultaneous power injection at sunny moments may cause a serious voltage rise along the feeder. These overvoltages may not only damage critical loads but also switches PV inverters off causing loss of green energy at the most productive moments. This paper presents a method to limit the voltage rise by introducing small battery buffers at local production sites. A smart inverter decides whether the PV energy is injected in the grid or buffered in the batteries. The relation between battery buffer size and overvoltage reduction is presented for a typical Belgian residential distribution feeder. The influence of the buffer along the feeder is calculated by working with synthetic load profiles and solar irradiation data.status: publishe