2What is an Inverter?A Solid State Device which main job is to convert a Direct Current Supply to an Alternating Current SupplyInverter Symbol
3An Inverter converts this Direct Current Input Wave Shape To this Alternating Current Output wave shape
4By using many very high speed switching devices an inverter is able to convert a series of precise D.C. Pulses into a synthesised A.C. Wave shape
5Inverter Principle of Operation Basically a 4 way switching bridge is used to re-route the direct current to alternate it at a set frequency through the load.
6The Roles of a Grid Connect Inverter To convert D.C. from the generating source Photovoltaic Array or Wind Turbine etc into an A.C. Wave that is then transformed and synchronised with the electricity gridMay Provide galvanic (voltage) isolation between the D.C. side and A.C. sidesTo extract the maximum amount of energy from the generating sourceCalled Maximum Power Point Tracking (MPPT)To log and display electrical data from the array such as Energy, Power Voltage Current, $ Income & CO2 offsetSystem monitoring and protection over: current, temperature & voltageEarth fault & arc fault detection etc
11PN Junction DiodesCathodeAnodeDiodes are semi conductor devices consisting of a PN Junction the P is the anode and the N is the cathode.When a positive charge is placed on the anode & negative is place on the cathode the diode conducts and is said to be forward biased. If a negative is placed on the anode and positive on cathode the diode is said to be reverse biases and the diode will not conduct
12Bridge Rectifier Converts A.C. Supply in to Basic D.C. Supply SymbolInput wave shapeBridge RectifierOutput wave shapeBridge Rectifier
13MOSFET Transistor Metal Oxide Semi Conductor Field Effect Transistor Two N type semi Conductors within a P type baseWhen the gate is pulsed positive a electron bridge is created and current can flow through the source and drain.MOSFET symbol
15IGBT Insulated Gate Bipolar Transistor The insulated-gate bipolar transistor or IGBT is a three-terminal power semiconductor device, noted for high efficiency and fast switching. It switches electric power in many modern appliances: electric cars, variable speed refrigerators, air-conditioners, and even stereo systems with digital amplifiers. Since it is designed to rapidly turn on and off, amplifiers that use it often synthesize complex waveforms with pulse width modulation and low-pass filters.
16Double Wound Transformer Used for stepping the input voltage up or down providing galvanic isolation and helps with smoothing out the sin wave
17Types of Wave Shapes of Inverters Square WaveNo voltage regulation, cheap and nasty, limit to type of appliances that can be run off itModified Square Wave voltageStill a square wave except the voltage is Regulated by Pulse Width Modulation (PWM)True Sin wave (PWM with filters) less than 5% total Harmonic Distortion
19Pulse Width Modulation to create a True Sine Wave Pulse width modulation is a technique used to create sinusoidal wave from a series of coded D.C. pulses called a pulse train. For the pulse train to becomeSmooth like a true sin wave a capacitive inductive filter must be used.
20Classifying Grid Connect Inverters Method of CommutationLine CommutatedSelf CommutatedTransformer/ TransformerlessHow P.V. Array and Inverter InterfaceModular (at the modules)String InverterMulti StringMini CentralCentral
21Line Commutated Inverters Using a thyristor Bridge arrangement the thyristor’s are switched (commutated)By alternated pulses from the grid.These are known as grid controlled inverters and when the grid falls these inverter will automatically stop
22Self Commutated Inverters Same Principle as Stand Alone InvertersUsing Pulse width modulation switching devices are MOSFET’s or IGBTMust be used with a Grid Protection DeviceTo ensure safety of the line workers when the grid goes down.
23Transformer Classifications Based on Transformers Low Frequency Transformer (Safe, reliable, lowest efficiency very heavy) Galvanic Isolation
24HF InvertersHigh Frequency Transformer (Galvanic Isolation, no iron Core, Tx very light and more efficient than Low Frequency Tx more complicated electronics)
25Transformerless Grid Connect Inverters No Tranformer (transformerless) (No galvanic isolation cheap to build most efficient has some serious safety concerns)