Reading a converter schematic

Understanding what the basics on converter schematic refer to in asset health

Electrical systems in a wind turbine are complex and may be new for many people.  At the end of the day, a wind turbine needs to convert mechanical energy into electrical generation.  A converter enables the conversion of the variable frequency output of the generator (driven by a variable speed wind turbine) to a fixed frequency appropriate to be provided to the grid or load.

A little background information:




Ohm is the electrical unit used for measuring resistance. Unit is denoted by Ω.


This is a unit of power. It is denoted by W


It is the difference in electrical potential between two points. Unit is denoted by V


A method in which the current flow happens. In Alternating current is the direction periodically changes. It is denoted by symbol


A method in which the current flow happens. In Direct current, the current travel direction is constant. It is denoted by  symbol.

Active Power

Power which is really utilized and consumed for useful works in AC or DC circuit. It is also called as True Power, Real Power. It is denoted by P and measured in W.

Reactive Power

Power which bounces back and forth between source and load in the circuit. This power is critical for transformers, motors to produce magnetic fields enabling actual work to be done. Reactive Power is denoted by Q and measured in VAr (Volt Ampere Reactive).

Power Factor

It is a ratio of working power to apparent power. It is measured in kVA. In DC circuits it is 0 due to zero frequency. In AC circuits it is a value between 0 and 1.

As the power generation goes, the steps are:

Components of an electrical system including: 

  • Generator side converter (abbreviated as INU) 
  • Grid side converter (abbreviated as ISU) - transfers the energy from the converter DC link to the grid and vis-versa
  • Insulated-gate bipolar transistor (IGBT) Supply Unit 
  • Various controllers
  • DC Link Capacitor - energy storage to manage voltage variations
  • DC Chopper - DC link power dissipation.  This is part of the system if grid ride-through is required
  • Filters (such as LCL filter) to suppress and manage harmonics
  • Main Breaker (MCB1), Converter contactor (MCB2), Stator Breaker (MCB3)

Please note that several of these components are often collectively referred to as 'the converter' system.