Semiconductors & Actives

Max Peak Power Trackers Increase efficiency of solar panels in Street Lights

street lighting in the accounts of many municipalities around half of the electricity expenditure. In addition to energy costs, replacement and maintenance of low pressure sodium or metal halide lamps metal present additional costs and disruptions of traffic. High-brightness LED (HBLED) on the basis of the solar street illumination does not depend on the electric power grid and have the potential to save billions of dollars in electricity costs and maintenance. Despite their power, solar street lights are not commonplace because of their price compared to traditional solutions. Nevertheless, like the world is looking for greener alternatives, solar powered street lights continue to benefit from advances in the field of target = “_blank”> Semi-conductors, in both photovoltaic and microcontrollers, to produce more cost-effective implementations.While that the sun shines up to 1000 watts per square meter, a typical panel can convert only 30% of radiant energy to electricity. In most of the street lights, energy harvested per day should be stored in a battery and use the conventional charge controllers may result in additional conversion losses. As solar panels are pn junctions, they do not work as ideal energy sources. In Instead, they have an operating point at which the energy is at its maximum and any movement away from that point will progressively decrease panel efficiency. To extract all the energy that the solar panel is capable of providing a fully electronic system called Max Peak Power Tracker (MPPT) is required. The MPPT is a DC-DC converter-which presents itself as an optimum load for the panel to function at its state power peak. Since the Max Peak Power Point (MPP) depends on the amount of radiating light and temperature of the panel, the MPPT must constantly adapt to maximize energy conversion.

Due to the characteristics of the panel, the current delivered is stable before falling dramatically Once the operating voltage has been adopted. The energy produced by the panel (x voltage current) is highest at a specific point on curve is called the point of knee. When a conventional controller without an MPPT is used to charge the 24V battery, the operating voltage of the PV panel is forced to the battery voltage and consequently the power produced by this facility is approximately 140W particular. A MPPT other hand, the group will operate at the point of the knee to the power equivalent to 215W. In this particular example, the use of a MPPT increases the total power of 50% harvested. Neglecting the losses in cabling and electronic load regulators and fuses, current battery charge in the above scenario is 8.5A ((x VPV Group Panel VPI) / VBATTERY = (41V x 5A) / 24V) while the current solar panel is the location panel solar 5A.The knee point changes continuously depending on factors such as the amount of light irradiating available, room temperature and partial shade. Therefore, a reliable MPPT must constantly update itself to operate at the ideal place to vary. A MPPT actively able to detect the voltage and current can measure the power and, through an iterative process and corrective arrive at the point of max.

The slope zero point on the curve always results in extracting maximum power from PV panel. The value of Itrim is varied proportional to the magnitude of the slope to allow the system is rapidly approaching that point. Such an algorithm allows the MPPT successful “hunt” for the optimal operating point while agnostic to any group and environmental characteristics.

Topology DC-DC conversion used by the MPPT depends on the voltage difference operation between the PV panel and battery. Under normal load, if the panel voltage is higher than the battery, a buck topology is used. Conversely, if the panel voltage is lower, Boost topology increases the charging voltage with a reduced current. In both cases, the objective of the MPPT is to maintain the current extracted from the PV panel at the climax. This relationship is given as PV = V MP (elbow) I × PV (elbow) battery = V × I + conversion losses of the battery. IBattery or load current depends on the duty ratio of DC-DC converter that is set by the regulator based on the algorithm MPPT.

The charge controller must also take into account the type of battery being used. street lighting applications typically use lead acid batteries, acid or alkaline is due to their high energy density / cost and the ability to operate over a wide temperature range. The voltage of these batteries must be constantly monitored during the charging process to avoid an overload can cause damage in the form of leaks or explosions. Similarly, an underestimation of a battery for long periods of time can significantly reduce the overall capacity of the battery. To avoid any degradation occurs, the system may disconnect all charges until the content reaches a predetermined threshold load. Correctly implemented loading routines are key to the longevity of a battery. The system’s inherent ability to precisely control the current to the battery throughout the day provides a peak load routines and diagnostic functions. When the amount of radiation reduced at dusk the member of the PV panel will reduce until the energy can not be effectively collected from the panel. This condition corresponding to the ambient light decreases can be detected by the system eliminates the need for an ambient light sensor. Once the operation MPPT is suspended, the system can automatically switch to the conduct of the source.

High brightness LEDs are very popular today light sources for lighting applications. Increase their efficiency, low maintenance cost and the ability to reproduce a variety of color temperatures are the reasons for their rapid adoption. frequent replacement of bulbs is very expensive and improved scope of life HBLED light engines is an impetus behind their use. Floor lamps generally produce over 3000 lumens and have a large number High Brightness LED individually. Since the diodes are connected in series to reduce the current drift between the different strings, the net voltage Futures Chain LED is typically greater than the battery voltage. In such cases, a boost topology can be used to create a step-up converter. A switching step-up DC-DC converter operates on similar principles as the charge controller with LED String relationship × V I LED String = V x I -. Because battery battery conversion losses MPPT and LED driving require DC-DC converters, similar to constant current hysteresis controllers can be used for both models. An adjustable hysteresis controller with a fast response time can be used to create a buck or boost topology.

At the heart of the design is a system programmable chip (SoC) which uses the resources on board analog to continuously measure the VI characteristics of solar panels, batteries and Charging LED. SoC, as PowerPSoC contain built-in controllers and pilots hysteretic door for further integration thrust of the control loops.

The “PV hysteresis Buck Controller FET driver switches to keep abreast through regular contact with L1 ripple tight. A true hysteretic controller will compare the rising and falling edges of current programmable thresholds. The resolution of the current control is only limited by the speed of the chain of hysteresis and resolution of the digital-analog converters (DAC) that generate thresholds. Synchronous FET driver is used in the down circuit to increase the efficiency of the system. As an additional cost for efficiency compromise, the driver MOSFET and inductor L2 can be replaced by a Schottky diode flyback.

The ” LED Hysteresis Boost Controller “receives input from a high side current sense amplifier similar to the control of current through inductor Boost L3. Ultrafast diode D3 blocks the higher voltage to C3, which is used to drive the load LED. A proportional integral loop running the microcontroller system on chip for precise control of LED current. This pilot implementation with well-chosen ingredients can conveniently yield above 95% efficiency. Just the feature on a MPPT PV charge controller panel can significantly improve the ability energy recovery. Costs away from conventional charge controllers are immediately releaved by savings made in reducing the size of photovoltaic panels. In addition, the high degree of analog control to better the life of battery by reducing maintenance costs associated. Integration of different basic blocks in programmable SoC devices providing significant reductions costs and time to market. As the world marks the beginning of a green revolution, the lighting effective and independent Grid turns the roads of tomorrow.

Lecture 17 – Schottky Barrier Diode