Antti Kosonen

Power-line communication-based network architecture for LVDC distribution system

In smart grids, a communication network with bidirectional data transmission between network components is required for functionalities, such as grid monitoring, control and protection. These functionalities set different requirements for communication. This paper focuses on the use of power-line communication (PLC) as a data transmission method for monitoring, control and protection functions in a proposed novel smart grid concept - low-voltage direct current (LVDC) distribution system. Hence, a PLC-based communication architecture for the LVDC system is proposed, its feasibility analyzed theoretically and verified by measurements. Channel capacity and practical data transmission tests are performed in a laboratory environment. Finally, the suitability of the proposed network architecture for the LVDC system and its compliance with the set requirements are analyzed.

High-Power Solar Inverter Efficiency Measurements by Calorimetric and Electric Methods

In this paper, the results of a European efficiency measurement for a 250-kW high-efficiency grid-connected solar inverter are presented. The efficiency measurements are performed both by electrical input-output and calorimetric methods. Two measurement series with input voltage levels of 500 and 750 VDC are carried out. An open- and balance-type calorimeter system that can measure power losses up to 30 kW is introduced and verified by resistor tests. The measurement results and their uncertainty are analyzed and discussed.

A new approach to data transmission between an electric motor and an inverter

In electrical drives data transmission between a motor and an inverter is required due to sensors, installed at the motor, that are used in the motor diagnostics or controlling. Generally, the data transmission is carried out using additionally installed cabling, such as, twisted pairs. In this article a new method is proposed that provides an Ethernet based communication link between the electric motor and the inverter. The method uses a motor feeder cable as a media and power line communications (PLC) as a communication method. Laboratory measurements with the method are carried out and the results of the measurements are analyzed

PLC Concept for LVDC Distribution Systems

The basis for smart grids is the implementation of active functionalities that interconnect the power system stakeholders, such as electricity end users (customers), producers, retailers, and system operators in a novel manner. Not only electric energy but also data flows are required between all the actors involved. A communication network between components and actuators is needed for functionalities such as grid operation, monitoring, and protection. This article studies powerline communication for a low-voltage direct current distribution system. An LVDC system is considered as part of future smart grids. The channel characteristic measurements carried out for an LVDC laboratory setup and the subsequent theoretical and practical analysis show that the studied LVDC distribution system provides a suitable medium for the high frequency band PLC between 5 and 20 MHz when an inductive PLC signal coupling method is used. Moreover, the article proposes an IP-based PLC network concept for the LVDC system; the concept is based on commercial industrial compliant HF band PLC modems.

Design considerations for current transformer based energy harvesting for electronics attached to electric motor

Energy harvesting or scavenging from environment is being researched intensively. The main motivation of the research is to develop a maintenance free energy source for ubiquitous electronics, such as wireless sensors or sensor networks. The on-line condition monitoring of electric motors requires also sensors that are installed at the motor. In this case, the energy required by sensors could be harvested from a magnetic field. In this article, current transformer based energy harvesting is considered. A switch-mode power supply utilizing current transformer is designed. It is tested in laboratory with the mains supply and variable speed drive. According to the tests carried out, the current transformer based power sources are a feasible alternative to supply the electronics attached to an electric motor.

Loss Definition of Electric Drives by a Calorimetric System With Data Processing

An accurate measurement of power or heat losses of high-efficiency electrical devices is difficult with input and output powers. In the calorimetric method, these losses are measured directly. In this paper, a functional heat loss measurement concept with adequate data processing methods is suggested for heat losses up to 2 kW. Such a heat loss range can be applied to present-day power electronic converters with the rated power of up to 110 kW and motors up to 37 kW. The measurement system does not require a complex mechanical structure or a large footprint area on the measurement site. The concept is scalable to different sizes. New features to the balance type calorimeter data processing are introduced. These include a mass flow correction, a technique to detect the thermal equilibrium, and a method to correct measured heat losses to improve the measurement repeatability and reduce the measurement uncertainty. The measurement uncertainty of the proposed calorimetric concept is 0.4%. Laboratory measurements are carried out both for a commercial frequency converter and an electric motor. These are measured at the same time with two calorimeters. The losses of these devices are measured both by the input-output and calorimetric methods.

Communication Concept for Sensors at an Inverter-Fed Electric Motor Utilizing Power-Line Communication and Energy Harvesting

In this paper, a novel communication concept for sensors at an inverter-fed electric motor is proposed. The concept utilizes power-line communication and a motor cable in data transmission. The signal used in communication is inductively coupled to the motor cable. The supply power for sensing and communication at the electric motor is harvested from the motor-phase conductor with a current-transformer-based power supply. The proposed concept has numerous advantages, such as no galvanic connection to the motor power circuit, an opportunity to implement the concept afterwards without electrical installation, and reliable and battery-free operation. The operation of the concept is analyzed, simulated, and verified by laboratory measurements.

Power Line Communication in Motor Cables of Inverter-Fed Electric Drives

It has been shown that an inverter-fed power line is a feasible medium for the transmission of modulated information. The communication channel includes the feeder cable terminated by two loads: the motor and the inverter. This link is a suitable alternative for the sensor cabling between motors and inverters in motor control and diagnostic applications. The use of the motor power cable in the speed feedback induction motor control application and the modelling of the formed communication channel are presented and discussed in this paper.

Noise analysis of a power-line communication channel in an LVDC smart grid concept

It has been shown that high-frequency (HF) band power-line communication (PLC) is a suitable data transmission method for the smart grid concept, namely a low-voltage direct current (LVDC) distribution system. In this paper, the PLC channel analysis in the LVDC system is continued with a detailed noise analysis. Noise signals from the terminals of PLC couplers are measured in the time domain. Noise power spectral densities (PSDs) are derived from the measured noise voltage, and the variation in the noise PSDs in the time domain is analyzed. The effects of noise on the performance of the HF band PLC are analyzed theoretically and by communication tests. The noise voltages are measured, and communication tests are carried out both in the LVDC laboratory system and in an LVDC field pilot system. The noise PSD is observed in the frequency band between 100 kHz and 30 MHz, which covers the band applied to the PLC in the channel. The results show that noise (mainly impulsive) in the channel has a major effect on the performance of the PLC.

Power line channel modelling for industrial application

Motor feeder cable has been shown to be a promising communication medium between the motor and the drive in motor diagnostics and controlling. The communication channel can be used for data transmission from the sensors installed at the motor to the drive or to the control PC. This article deals with both frequency (100 kHz - 30 MHz) and time- domain channel modelling in inverter driven electrical drives.