What is Power Line Communication?

Energy Generation and Consumption:

Today, Smart Energy has become a much-publicized buzzword. It could describe anything from energy production, to efficient use of that energy. As we will shortly see, PLC plays a vital role in making our energy practices ‘smart’.

PLC in Energy Generation

Renewable energy is growing at a brisk rate, having showcased a growth of 35.2% in 2010. A bulk of this growth came from a near doubling of Photovoltaic (PV) installations around the world. Further contribution came from increase of installed wind energy capacity; for instance in 2010 China grew its installed capacity by 64%.

In order for a Distributed Generation (DG) system to supply the grid power, its DC output must be converted by an inverter into clean, reliable AC power. Thus a typical DG system consists of the Energy production device (for e.g. the solar panel, the wind turbine, an electric vehicle), the inverter, the cabling and the communications. If we consider the specific case of solar power generation, until recently, most PV installations used central inverters or string inverters, in which case the performance of the system could be monitored with a few say, Ethernet connections to the inverters.

Today, there is a growing trend towards micro-inverters and power optimizers. These function at an individual solar panel level, and most suppliers provide monitoring capability for each of these modules. This provides vital performance statistics over the lifetime of the solar panel, and this can be used to detect and pinpoint performance issues. To implement such monitoring capability, one could use wireless – Zigbee, Wi- Fi, RF, and Bluetooth; or wired – PLC, RS-485, RS-232, and Ethernet, among others. In the case of micro-inverters, the implementation of a wireless solution can be challenging because of:

* Its line of sight requirement – micro-inverters are generally located behind a solar panel

* More complicated installation

* EMI problems

Alternatively, other wired technologies involve extra cabling and thus greater installation and maintenance costs. PLC can be both simpler and more economical.

Above we see the typical building blocks of a micro-inverter. The CY8CPLCxx chip, complete with PHY, network protocol and programmable application layer, has additional resources that allow for taking external sensor input. Thus vital parameters like temperature at each module, maximum power point, potential faults, and power generated can be monitored. Through the power line, these statistics can be viewed locally on an LCD display, or even remotely via the web. In case of faults, each micro-inverter can be switched off individually. Under-performing units can be repaired or replaced. Importantly, with PLC, installation and maintenance is simple and economical because of no additional sockets/wiring required – just plug and play. From the point of view of an equipment manufacturer, designing PLC into the system is straightforward because of Cypress’ certified and tested reference designs.

PLC in Energy Consumption markets

It is estimated by 2020, Europe will have 80% coverage of smart meters and the rest of the world is expected soon to follow suit. PLC is the predominant communication method in Automatic Metering Infrastructure (AMI) and also is being rapidly adopted in other applications. In this section, we will discuss the energy consumption market from two perspectives, namely:

• Auxiliary   Interface
• Smart Grid – AMI, Smart Appliances and V2G
• Other applications – Two examples will be discussed here –Data center power distribution and Lighting control.

Smart Grid

Mr. Carnegie, waiting for his flight at the San Francisco international airport, browses through his inbox on his smart phone, when he receives a mail from the local energy provider informing him about peak pricing coming into effect in the next four hours, back home in Dallas. He knows that his Air Conditioning will turn off automatically during this time. Knowing the electricity rates at this hour, he decides to check up on his solar panels by just a touch on his smart phone screen. While this may seem to be science fiction, smart grids, empowered by PLC solutions, are making it a reality.

The ‘Smart Grid’ is essentially modernization of the transmission and distribution aspects of the electrical grid. This intelligent power distribution infrastructure enables two-way communication between the consumers and the utility. The consumers use home networks to communicate with their smart meter, which further communicates with the utility (Advanced Metering Infrastructure-AMI). The Smart Grid definition does not stop at energy utilization; supply of energy to the grid from Distributed Generation (DG) sources such as solar and wind fall into the same category. The DG system also includes Vehicle-to-Grid (V2G) - bi-directional sharing of electricity between Electric Vehicles (EVs) and Plug-in Electric Hybrid Vehicles (PHEVs) and the electric power grid. In this article, we will talk about AMI, Smart Appliances and V2G.

Advanced Metering Infrastructure:

The whole measurement and collection system that includes meters at the customer site, communication networks between the customer and a service provider, such as an electric, gas, or water utility, and data reception and management systems, that make the information available to the service provider, are referred to as AMI. The Smart Meters transmit the collected data through commonly available fixed networks such as Power Line Communications (PLC), Fixed Radio Frequency (RF) networks, and public networks (e.g. landline, cellular, paging) which is aggregated by a concentrator, sent to the utility and then to a Meter Data Management System for data storage, analysis and billing (see Figure 3). Studies show that Narrowband PLC is best suited for AMI with over a 100 million NB-PLC devices installed to date.

Utilities are investing billions of dollars in AMI systems. PLC solution for data transmission needs no new infrastructure, unlike wireless, as it uses the existing power cables. Power line carrier systems have long been a favorite at many utilities because it allows them to reliably move data over an infrastructure that they control. Utilities may also use public cellular as the backhaul for the AMI data due to its footprint, zero implementation cost and low monthly fee. But on many occasions they may not be able to provide 100 percent coverage of a utility’s entire customer base.

Alternatively, using wireless networks, RF solutions or PLC for data transmission will solve this issue. Rural utilities or the utilities located at challenging locations (for e.g. mountainous terrains) which are ill-served by wireless will have a difficulty communicating with the consumers. Additionally, wireless and RF solutions have reduced data rates in presence of interference like Bluetooth devices, cordless phones, concrete objects, hills and even trees. PLC can communicate to any location connected via the power line and has no line-of-sight requirement for data transmission. One of the most important considerations, due to the volume of network traffic inherent to the smart grid network, is congestion mitigation. As compared to wireless solutions based on ZigBee or Wi-Fi, PLC-based AMI have a proven track record of being better suited to avoid network congestion in emergency situations. Another oft cited requirement is that of redundancy in the communication channel – with the ubiquity of power lines, deploying a redundant channel becomes more economical.

Various applications would include remote monitoring, outage management (which includes fault detection of MV equipment), Demand Response (i.e. managing customer consumption of electricity in response to grid supply conditions), island detection (i.e. ensuring that local grids are not being powered by the DG system when there is no power present from the electric grid) and fraud/theft detection.

Smart Appliances:

A Home Area Network (HAN) is a communication-enabled home where all electrical appliances are connected in a mesh through Wireless, RF or PLC. Electrical appliances, today, are connected in a network with two-way communication enabled, with each other as well as the substation. These Smart Appliances allow automation and control from single or multiple access points.

In the chart above (See Figure 5) you will observe the estimated revenues (US $M) in 2011 made by Smart Appliances (Source: Zpryme Research & Consulting) and is projected to grow with a CAGR of 49% from 2011 to 2015.This gives an insight to the potential that this industry holds.