Observer Based Sensor Fault Tolerant for Grid Tied - Solar Inverters

Grid-tied Solar Inverters rely heavily on the current sensor information to fulfill all the complex tasks associated to deliver appropriate power to the energy system with low distortion. Sensing voltage and current are an essential part of the feedback current control loop for any grid tied-solar inverter. When the sensed signal is lost, the inverter output could become unstable thus having, as a consequence, over-current situations, and other undesired power generation conditions that could lead to the catastrophic failure of the inverter. To overcome this issue, a fault-tolerant system is proposed using an observer structure designed as a way to make a 3 phase inverter current control system immune to any fault or lost of its sensing capabilities. The sensor verification is made by a smart control capable of monitoring the physical sensor operation and switch to the synthetics sensors in case of physical damage of the equipment. The proposed technique is verified by inserting a sensor fault in the system. Under this condition a good performance of the proposed fault tolerant structure is observed. The fault tolerant scheme is able to follow and determine the sensing signal lost or corrupted and seemliness continue the operation of the inverter, notified of the fault situation and wait planned shutdown is scheduled.