Photovoltaic Systems Engineering Session 10 SEC598F18 Photovoltaic Systems Engineering Session 10 Electronic Control Devices (ECDs), Part 1 Charge Controllers October 01, 2018

Session 10 content Charge Controllers Purpose, utility Operation, reliability, failure mechanisms

Learning Outcomes Introduction to the power electronics used in PV systems Recognition of the importance of controllers to the operation of certain PV systems

PV Systems - Batteries Lead Acid Battery Lead acid batteries are less prone to electrolysis and sulfation if the charging protocol does not employ a constant rate. The optimized charging profile looks like this: This current profile is produced by a “charge controller”

PV Systems – Charge Controllers A simplified version of a “stand-alone” system that transfers DC electrical energy to a storage device

PV Systems – Charge Controllers The charge controller is an essential electronic component in any PV system that employs battery storage The charge controller carries out some important functions: It accepts the DC power from the PV array It directs the DC power to the battery array matching the optimal charging procedure, as needed It directs the DC power to the inverter for the AC standby loads or grid connection, or to DC electrical loads

PV Systems – Charge Controllers These features must be met in the choice of charge controller: Its DC output must match the battery array voltage Its DC output must normally supply enough current to recharge the battery array in one day Its DC current directed to the inverter must not exceed the allowable inverter input There are quite a few Charge Controller manufacturers with very high quality products

PV Systems – Charge Controllers Pulse Width Modulation (PWM) An electronic technique that is used to: switch from an input dc voltage at one level to an output level at another level, as in DC power supplies carry out the ‘perturb and observe’ process to find the maximum power point generate time dependent voltages that closely approximate sinusoidal or other waveforms

PV Systems – Charge Controllers Pulse Width Modulation (PWM) AC-DC converter DC-DC switching power supply ac line voltage rectifier

PV Systems – Charge Controllers Pulse Width Modulation (PWM) – Duty Cycle Vm v(t) Vavg ton toff time

PV Systems – Charge Controllers Pulse Width Modulation (PWM) – Duty Cycle

PV Systems – DC-DC converters Boost converter The transfer characteristic is: en.wikipedia.org/wiki/Boost_converter

PV Systems – DC-DC converters Boost converter ON OFF

PV Systems – DC-DC converters Buck converter The transfer characteristic is: en.wikipedia.org/wiki/Buck_converter

PV Systems – DC-DC converters Buck converter

PV Systems – DC-DC converters Buck-Boost converter The transfer characteristic is: en.wikipedia.org/wiki/Buckboost_converter

PV Systems – DC-DC converters Buck-Boost converter

PV Systems – DC-DC converters Summary Boost Converter Buck Converter Buck-boost Converter

PV Systems – DC-DC converters Summary Boost Converter Toyota Prius LED Lamps Buck Converter Impedance matching Charge controllers Buck-boost Converter

PV Systems – Charge Controllers 12V, 24V, 48V 45A, 70A, 100A 1600W, 3200W www.morningstar.com

PV Systems – Charge Controllers Charge controller block diagram Isolation of PV array and battery Protection from overcharging Protection from deep discharging www.morningstar.com

PV Systems – Charge Controllers Charge controller operation www.morningstar.com

PV Systems - Maximum Power Point Tracking The PV system produces electrical power and is best utilized when the maximum power produced can be fully delivered to the electrical “load” – this can only happen when the power source and the power load “match” C.S.Solanki, Solar Photovoltaic Technology and Systems