Antti Pinomaa

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.

Research Site for Low-Voltage Direct Current Distribution in a Utility Network—Structure, Functions, and Operation

This paper introduces a research site for a low-voltage direct current (LVDC) distribution system. The research site was established to enable practical studies concerning different areas of the LVDC distribution. Because the LVDC distribution is a novel approach to public electricity distribution, the objective is to combine a fully functional LVDC system and a flexible research platform, where various measurements and tests can be conducted. The scope of this paper is to discuss the design, structure, functionalities, and operation of the site. Experiences of use and measurement results are provided to demonstrate the major functionalities and other important system properties. Finally, future research tasks and the development of the site towards the LVDC μGrid are presented.

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.

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.

On Common-Mode and RF EMI in a Low-Voltage DC Distribution Network

This paper addresses common-mode (CM) and radio frequency (RF) electromagnetic interferences (EMI) in a converter-fed low-voltage direct current (LVDC) distribution research network. The LVDC distribution is a novel approach to public electricity distribution, and a research site is set up to enable comprehensive studies concerning the LVDC distribution. Because the customers in the LVDC system are supplied with customer-end inverters (CEI), CM and RF EMI generated by the CEIs have to be analyzed. To this end, common-mode currents in the DC network and the customer-end networks are studied by on-site measurements. The objective is to determine whether there are disturbances that exceed the requirements of the standards or whether the CM current could cause safety issues in the converter-fed user-end network. In the DC network, the effect of the CM current on the feasibility of power line communication (PLC) in a DC network is analyzed. Finally, RF disturbances are measured and discussed.

Utilization of Software-Defined Radio in power line communication between motor and frequency converter

In this paper, a power line data transmission link based on Software-Defined Radio (GNU Radio) for motor cable communication between an electrical motor and a frequency converter is developed and tested. The test environment includes a frequency converter, an electrical motor (2.2 kW), and a 90-meter-long motor power cable. Two differential phase shift keying (DPSK) modulations, DBPSK and DQPSK, are used and their performance is compared with and without forward error correction (FEC). Experiments prove that GNU Radio with USRP (Universal Software Radio Peripheral) is a competent platform to be used as a testing and developing power line communication applications.

Applicability of narrowband power line communication in an LVDC distribution network

It has been shown that high-frequency (HF) band power line communication (PLC) is a feasible data transmission method for a smart grid concept, namely for a low-voltage direct current (LVDC) electricity distribution system. However, because of the signal attenuation, the communication distances in the LVDC grid are limited with the HF band PLC. Hence, the new narrowband (NB) PLC should also be tested for the concept. In this paper, the PLC channel analysis in the LVDC system is carried out for the novel NB PLC technology, that is, the G3-PLC in the frequency band of 150-490 kHz. For the channel analysis, channel gain and noise signals from the terminals of the PLC couplers designed for the NB PLC are measured. The performance of the G3-PLC is analyzed theoretically and by communication tests. The noise voltages are measured, and communication tests are carried out in the LVDC laboratory system and in an LVDC field installation grid. The results show that NB PLC could be suitable for the concept.

Control and monitoring solution for the LVDC power distribution network research site

This paper introduces and describes a control and condition monitoring system of a low-voltage DC (LVDC) public electricity distribution network. To enable practical studies concerning the LVDC distribution system, a research site was built by Lappeenranta University of Technology (LUT) and a Finnish distribution system operator Suur-Savon Sähkö Oy. To enable secure operation of the research site, a condition monitoring system was developed. It comprises system supervision and control for both normal operation and emergency situations. Moreover, network power quality monitoring functions are implemented to monitor the quality of supply and system reliability in general. In the paper, the condition monitoring, information, control, and diagnostic functions of the developed management system are described.

Channel model for a power line communication medium in an LVDC distribution system

It has been shown that power line communication (PLC) in the high frequency (HF) band is a feasible data transmission method for a future smart grid concept - a low-voltage direct current (LVDC) distribution system. Furthermore, PLC is proposed as a basis of the data network architecture in the LVDC system. In the analysis of the communication channel characteristics and the design of the communication system, channel modeling plays an essential role. A PLC channel model in the LVDC system is presented and analyzed in this paper. The channel model is implemented with a circuit simulator, which provides several advantages for the modeling; for instance, channel characteristics can be analyzed and modeled both in the time and frequency domain. In this paper, the PLC channel gain (including signal attenuation in the power cable) in the LVDC system is modeled in the frequency domain. The channel model is verified by and compared with measurements carried out in the PLC channel in an LVDC laboratory system.

Common-Mode and RF EMI in a Low-Voltage DC Distribution Network With a PWM Grid-Tie Rectifying Converter

In this paper, common-mode (CM) and radio frequency (RF) electromagnetic interferences (EMIs) in a low-voltage direct current (LVDC) distribution network are investigated. LVDC being a novel approach to public electricity distribution, a research site was set up in a public rural-area distribution network to enable comprehensive studies concerning the LVDC distribution. In a previous journal article by the author, CM and RF EMI were studied with the objectives: (1) to determine whether there are disturbances that exceed the requirements of the standards, or whether the CM current could cause safety issues in the converter-fed user-end network; (2) to discuss the effects of the CM current on the feasibility of power line communication in a dc network; and (3) to analyze the measured RF disturbances. However, standardization is still lacking for the frequency range from 2 to 150 kHz. In this paper, in situ measurements are conducted on the LVDC research site to define the levels of disturbance. The results in the previous journal article were based on the research site with a thyristor bridge rectifier, and when the rectifier was upgraded to a PWM grid-tie rectifying converter, disturbances were measured again. In this paper, these results are analyzed against the previous measurements to define whether additional measures are required. Further, the design and implementation of a CM filter and its effects on the disturbances of the dc network are analyzed.