Examples of energy-efficient solutions for smart grids

Many market research institutions predict that by 2030, the share of renewable energy (such as wind power and solar power) in the total global energy consumption will increase significantly. The advocacy of energy conservation, emission reduction and green development has put forward new requirements for all industries. Energy-saving design that caters to the low-carbon economy era has become an important manifestation of the competitiveness of energy companies and electronic products.

Market opportunities and challenges

The development of renewable energy is an irresistible trend. Solar and wind power are components of smart grids and belong to the category of distributed power generation. Promoting the development of smart grids can bring many advantages, such as using two-way communication to achieve demand management, ease peak power consumption, quickly discover faults, avoid power outages, and achieve higher energy efficiency, reliability and safety; intelligently integrate new alternative energy sources and provide power for electric and hybrid vehicles; better adjust energy supply and demand, use power plants and power grids more efficiently, and reduce carbon emissions; provide dynamic rate tables to help customers optimize total power consumption and electricity bills, improve customer service; and remote meter reading and remote power on and off can save labor costs and improve operational efficiency.

Under the consensus of promoting sustainable development, China is currently vigorously developing industries such as solar energy and wind energy, and the prospects are promising. Among them, the technology in the field of solar energy has become increasingly mature, and solar power generation has made great progress. Solar street lighting is also becoming more and more popular. In addition, in order to introduce a new generation of smart grids and improve the power infrastructure, the Chinese government has set a grand goal of investing 4 trillion yuan by 2020, and the concept of "Strong & Smart Grid" has been demonstrated at the Shanghai World Expo.

However, there are also many challenges in developing renewable energy and upgrading the existing power grid. For the semiconductor industry, the biggest challenge is energy conversion, because the key to developing renewable energy is to optimize energy efficiency. Take solar-powered LED street lighting as an example. This application requires efficient and reliable solar panel charging controllers, as well as key devices such as LED drivers, and the demand is considerable. Smart grids also require many electronic components from power generation, distribution and field area networks to smart meter communications and home area networks. These include power factor controllers, AC-DC and DC-DC controllers, regulators, MOSFETs, triacs (TRIACs), power line carrier modems, filtering, input/output (I/O) and data protection, line drivers and signal amplifiers, LCD backlight drivers, EEPROM memories and smart card interfaces.

Examples of energy-efficient solutions for smart grids

1. Solutions to improve the photoelectric conversion efficiency of solar panels

In recent years, the industry has paid more and more attention to street lighting using renewable clean energy solar energy. For solar street lights, it is very important to improve the photoelectric conversion efficiency of solar panels. The voltage-current (VI) characteristic curve of solar panels is nonlinear and variable, and it is very difficult to obtain the maximum amount of electricity from them. This requires the charging controller and other related electronic circuits of solar LED street lights (generally implemented by microcontrollers) to use effective control methods as much as possible to improve energy efficiency.

ON Semiconductor's CS51221 enhanced voltage mode PWM controller is a device that can improve the energy efficiency of solar panels. It can control the charging of solar panel batteries, support the maximum peak power tracking (MPPT) function, provide compensation for the changing VI characteristic curve of solar cells, optimize the power output of solar cells, improve energy efficiency, and charge the battery to the optimal power.

In the application circuit, it is necessary to select a suitable topology for the CS51221. The topology should be able to reduce the solar panel output voltage to 12V in the case of one battery, and can be easily modified to support boosting to 24V in the case of two or more batteries. The CS51221 itself can be configured as a forward, flyback or boost topology. In the reference design for solar panel charging control applications, ON Semiconductor chose the flyback topology.

In the application, the maximum peak power tracking function is implemented by dynamically adjusting the current limit at the ISET pin. Once the input voltage drops pulse by pulse, the current limit will be reduced until the input voltage recovers. This method does not require the use of an expensive microcontroller. The charge controller implemented in this way will find the peak power point and dynamically adjust it to match the changing power characteristics. In fact, by using the maximum peak power tracking technology, 30% more charge can be transferred from the solar panel to the battery than before, so that the solar street light system can use smaller solar panels, which brings significant cost benefits. Figure 1 is a schematic diagram of the solar panel charging control application using the ON Semiconductor CS51221 controller.

Figure 1: Solar panel charging control application using ON Semiconductor CS51221 controller

In addition, ON Semiconductor's NCP3066 constant current buck regulator can also be used in LED driver applications for solar street lights, providing the power and light output required by the system with extremely high energy efficiency.

2. Smart Grid Solutions

Today's power grid has become larger, safer and more energy-efficient than ever before, but its intelligence level is still relatively low, so smart grid is an important development trend today.

ON Semiconductor has invested and is investing heavily in smart grid research and development, covering all product lines, including power conversion analog ICs, signal ICs (such as low noise amplifiers), power discrete devices (high-voltage MOSFETs, IGBTs, rectifiers), mixed-signal ICs (smart card interface ICs, clock and timing ICs), communication ICs (such as PLC modems), logic ICs, memory ICs, and standard discrete devices (protection, filters).

The core of the smart grid is the smart meter. With the help of smart meters, power companies can know how much electricity users use and when, so that they can provide differentiated pricing and help users optimize their overall electricity consumption and electricity bills.

ON Semiconductor's solutions for smart meters include a series of standard products, application-specific standard products (ASSPs) and application-specific integrated circuits (ASICs), which can provide the four basic functions of smart meters, including power supply/power management, measurement, storage and communication. Figure 2 shows a smart meter application composed of various devices (green parts) from ON Semiconductor.

Figure 2: Smart meter application consisting of various products from ON Semiconductor

The fully integrated power line carrier (PLC) modem AMIS-49587 is a key device in the application of Figure 2. The device provides a highly integrated, standard-compliant low-power PLC solution that can be used in areas such as smart power automatic meter reading and management, street lighting control, smart power plugs, and building automation. AMIS-49587 uses ON Semiconductor's mixed-signal technology to integrate analog modem front-end and digital post-processing functions in one integrated circuit.

AMIS-49587 complies with the IEC1334 standard, which helps simplify design, reduce development and application costs, and speed up the time to market. The device is based on the ARM7TDMI processor core and includes a physical interface transceiver (PHY) and a media access controller (MAC) layer, while most competing solutions require complex embedded software to perform the same functions as the AMIS-49587. The device uses spread spectrum frequency shift keying (S-FSK) modulation technology, combined with precise filtering, to provide reliable low data rate communication for long-distance power lines, as well as a half-duplex adjustable communication rate of 2,400 bps (baud). The low operating frequency of less than 20 kilohertz (kHz) combined with the automatic repeater function makes communication more reliable and communication errors lower than other and existing solutions. Figure 3 is a block diagram of the AMIS-49587.

Figure 3: AMIS-49587 block diagram

Summarize

Driven by government energy-saving regulations and various energy efficiency programs, the renewable energy and emerging smart meter markets have great growth potential. In this process, semiconductor devices will shoulder the heavy responsibility with their comprehensive advantages of low energy consumption, high energy efficiency, high reliability, high speed, high intelligence and small size.

ON Semiconductor has a wide product lineup based on advanced technology and large production scale to meet the market opportunities and challenges of smart grids, including standard products, ASSPs and ASICs. The technology covers from extremely high voltage (700 V) technology (used to develop analog power conversion ICs in power supply/power management) to sub-micron 0.11 um CMOS technology (integrating microcontroller cores and mixed-signal analog circuits on a single silicon chip), as well as high-voltage MOSFETs, IGBTs and rectifiers.