Photovoltaic Systems Engineering Electronic Control Devices (ECDs) SEC598F17 Photovoltaic Systems Engineering Session 13 Electronic Control Devices (ECDs) Charge Controllers Inverters October 03, 2017

Session 13 content Charge Controllers Inverters Purpose, utility Operation, reliability, failure mechanisms

Learning Outcomes Introduction to the power electronics used in PV systems Recognition of the importance of controllers and inverters 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

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