Improving Efficiency in Smart Grid Applications With Fully Integrated Current Sensing ICs
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Application Information Improving Efficiency in Smart Grid Applications With Fully Integrated Current Sensing ICs By Shaun Milano Allegro MicroSystems, LLC, and Andreas P. Friedrich Allegro MicroSystems Europe Focus on the Photovoltaic System PV Systems The rising cost of fossil fuels, combined with a growing awareness of the need for low carbon emissions, have triggered intense research and development activities in technologies that use renewable resources. Renewable energy contributes 19% of global final consumption and has grown at double-digit rates annually for many technologies over the last five years [1]. In particular, windmills and photovoltaic (PV) solar technologies have been experiencing significant development, with grid-connected solar PV technology growing the fastest at annual rates of greater than 60% [1]. With increasing concerns about the global demand for energy and environmental awareness, power electronics applications are under pressure to improve efficiency. The advent of the Smart Grid, Plug-in Hybrid Electric Vehicles (PHEV) and full Battery Electric Vehicles (BEV), as well as grid-tied photovoltaic (PV) and other grid-tied renewable energy systems, all will require development of highefficiency inverters. In particular, new developments in the design of photovoltaic inverters are targeted at minimizing the cost-per-watt and increasing the maximum power harnessed from the solar system to deliver the best possible return on investment. Allegro™ MicroSystems LLC has developed a unique family of high performance integrated current sensor ICs designed to be used in Smart Grid inverter and motor control applications. The major challenge associated with solar energy production is the conversion of the DC currents generated by the PV panel to the sinusoidal AC current of the power grid. Figure1 illustrates a simple block diagram of the PV system and is comprised of a solar panel array and an inverter in a grid-connected configuration with switching control as well as maximum power point tracking (MPPT). MPPT modules Photovoltaic Panel Supply Side Load Side Utility Power Grid DC-to-DC Converter High Efficiency DC-to-AC 440 V Inverter Gating Signals Figure 1. Photovoltaic system diagram Current Sensor Circuit Breaker Control Panel Power Meter Loads Residential Commercial

are often employed on each PV string for larger arrays because the maximum power point can change continually from one solar string to another depending on variances in solar radiation. Current sensors are essential in tracking these DC current levels and a microcontroller is then used to adjust the system’s operating point to deliver the maximum power available from each PV string. A comparison of these current measurements is also useful in detecting deficient PV strings. The vast number of low power PV systems for residential use can also employ current sensors to control MPPT and...

developed a family of innovative, fully integrated, current sensor packages that are ideally suited for inverter applications that drastically improve the offset, sensitivity and bandwidth operation of Hall based current sensor IC’s. In each of the sensor packages, the IC itself is the most important component and contains a precision Hall-effect element that is coupled to a low-offset, high-accuracy amplifier. performance of the Hall IC output signal as shown in figure 2. The analog output response times of less than 4 μs allows sensing of higher frequency switching inverters. In...

• Since the Hall-effect current sensor linear IC is fully integrated it allows Allegro to factory program the device to compensate for zero amp and sensitivity variation over temperature. The block diagram in figure 3 shows that advanced features can be integrated into the device to reduce overall bill of material costs; for example, an overcurrent fault output that responds in < 2 μs with a user-programmable trip point. The fast digital fault output can be used to protect IGBT devices in case of over-current conditions. The internal conductor resistance is only 1 mΩ and provides for low...

References [1] REN21 Renewable Energy Policy Network for the 21st Century – Renewables 2010, Global Status Report – p.15 [2] IMS Research – PV Inverters, Annual report 2010 This paper originally appeared at the Smart Grid Forum in October 2011. Portions not copyrighted by Smart Grid Forum Copyright ©2011-2013 Allegro MicroSystems, LLC The information contained in this document does not constitute any representation, warranty, assurance, guaranty, or inducement by Allegro to the customer with respect to the subject matter of this document. The information being provided does not guarantee...