Windy Boy Protection Box - qrsrenewables.ie

Technical Information

WBP-UEN083910 Version 1.0 1/11

Windy Boy Protection BoxOvervoltage protection for small wind turbine systems

1 ContentsSmall wind turbine systems are reliably connected to the public grid or to a stand-alone system via Windy Boys. The Windy Boys operate with DC voltage on the input side. Subsequently, the frequency-variable output voltage of the small wind turbine system first needs to be converted into DC voltage. In addition, in order to protect the electronics and the Windy Boy from becoming damaged, the physical properties of a small wind turbine system require overvoltage protection in the system. The following occurrences can possibly lead to overvoltage:

• Wind gusts / storm• Sudden unloading of the Windy Boy due to grid failure or grid synchronization• Low energy demand from the stand-alone system in the event of high availability of wind energy

Technical Information General Specifications

SMA Solar Technology AG 2/11

The Wind Boy Protection Box consists of a rectifier and the power electronics for protecting against overvoltage. The Windy Boy Protection Box converts the variable AC voltage of a permanently excited synchronous generator of a wind or water turbine into DC voltage with which it supplies the Windy Boy. The integrated overvoltage protection protects the Windy Boy's input from damages resulting from resonant voltage step-up.In this document we present you with specifications, recommended system constellations and application examples.

2 General Specifications

2.1 Typical small wind turbine systemsIn general, a small wind turbine system in grid-parallel operation consists of the following components:

• Wind turbine including permanent magnet generator• Rectifier• Overvoltage protection and load resistor (dumpload)• Inverter incl. turbine control

Technical Information General Specifications


2.2 Small wind turbine system with components from SMA Solar TechnologyThe system configuration for a small wind turbine system with components from SMA Solar Technology looks as such:

Object DescriptionWind turbine Converts wind energy into electric energy. Due to the variable speed of the rotor and

the permanent excitation of the synchronous generator, the AC output voltage is generally variable in terms of both frequency and amplitude.

Windy Boy Protection Box

Converts the frequency-variable voltage of the wind turbine into DC voltage and contains the electronics of the overvoltage protection. The Windy Boy Protection Box is only functional in combination with the load resistor. Without a load resistor, the system has no overvoltage protection.

Load resistor The load resistor is absolutely necessary for the loading of the turbine during overvoltage so as to reduce the speed and thus the overvoltage. The electronics of the Windy Boy Protection Box control the power flow to the resistor.

Windy Boy Converts the DC voltage of the Windy Boy Protection Box into grid-compliant AC voltage. The Windy Boy also includes an intelligent turbine controller for the optimization of the energy yield.

Asynchronous generatorsSmall wind turbine systems with asynchronous generators are not suitable for operation with a Windy Boy and the Windy Boy Protection Box.

Technical Information Product Details


3 Product DetailsThe Windy Boy Protection Box is the interface between your small wind turbine system and the Windy Boy. It primarily consists of two main components:

• Rectifier• Intelligent overvoltage protection (requires an external load resistor)

A passive rectifier (B6 bridge) initially converts the frequency-variable AC voltage of the wind turbine into DC voltage. The built-in measuring equipment records this DC voltage. In the event a maximum DC voltage threshold is surpassed, the overvoltage protection is activated and the voltage is instantaneously contained.



3.1 Overvoltage protectionIn the event the input voltage of the Windy Boy reaches a critical voltage value, the wind turbine is additionally loaded through the load resistor. The input voltage is supposedly limited to the permissible value.The load resistor is deactivated when the lower preset voltage value is reached again. The procedure repeats itself if the voltage once again increases. If the voltage falls and generally remains below the critical threshold, the overvoltage protection remains inactive (see figure).

The voltage thresholds depend on the respective type of Windy Boy Protection Box. The input voltage of the Windy Boys is limited to the following values:

• WBP Box 400: limited to 360 VDC



Destruction of the Windy Boy Protection BoxThe Windy Boy Protection Box functions only in combination with a respective Windy Boy and a sufficiently sized load resistor. The electronics of the Windy Boy Protection Box will be destroyed during operation if the box is not connected to a Windy Boy and a load resistor!



3.2 Load resistorA respectively sized load resistor which is connected to the Windy Boy Protection Box is indispensable for the functionality of the overvoltage protection. The load resistor adds additional load to the wind turbine and converts the surplus electric energy into heat. The load resistor must be designed to handle a permanent load of the wind turbine. An optimally adjusted load resistor can be ordered from SMA Solar Technology.The load resistor is specially adjusted to meet the requirements of the entire system. Other resistors such as fan heaters, heater elements and rotational loads are not suitable for application with the Windy Boy Protection Box.The load resistor must meet the following requirements:

Nominal DC voltage: 600 VResistance value @ 25 °C surface temperature: approx. 30 OhmResistance value @ 80 °C surface temperature: approx. 42 OhmContinuous nominal power: 7,000 W

Destruction of the Windy BoyThe functionality of the overvoltage protection can be negatively affected through the connection of a non-suitable load resistor. This can lead to the destruction of the Windy Boy or the load resistor.

Technical Information Application Examples


4 Application Examples

4.1 Single-phase grid connection

In accordance with the figure illustrated above, the following constellation can be installed for the single-phase grid connection of a small wind turbine system:

Deterioration of the energy yieldThe compatibility of the wind turbine and the Windy Boy must be checked separately. It is mandatory that the DC output voltage of the wind turbine is compatible with the operating voltage of the Windy Boy.

Destruction of the Windy Boy Protection BoxAs a matter of principle, the Windy Boy Protection Box must not be connected in parallel on the DC side.

Small wind turbine system - system Windy Boy1 x wind turbine with max. 3.5 kW1 x WBP Box 4001 x load resistor

1 x Windy Boy 1100 or1 x Windy Boy 1700

1 x wind turbine with max. 5 kW1 x WBP Box 5001 x load resistor




4.2 Two or three-phase grid connectionThe three-phase connection of a small wind turbine system is either logical or mandatory for diverse grids, in different countries as well as for stand-alone grid systems. The Windy Boy Protection Box has the possibility to connect up to three Windy Boys. If this is the case, the Windy Boys can be operated in parallel.The following constellation can be installed for the three-phase grid connection of a small wind turbine system:

Small wind turbine systems with a capacity of up to 7 kW


1 x Windy Boy 2500 or1 x Windy Boy 2800i or1 x Windy Boy 3000 or1 x Windy Boy 5000 A or1 x Windy Boy 6000 A

Small wind turbine system - system Windy Boy1 x wind turbine with max. 3.5 kW1 x WBP Box 4001 x load resistor




Small wind turbine system - system Windy Boy



Small wind turbine systems with a capacity of 10 to 25 kW

As in the last section, possible constellations are illustrated for the three-phase grid connection of small wind turbine systems with a capacity exceeding 10 kW. It is possible to operate several Windy Box Protection Boxes in parallel.In accordance with the figure illustrated above, the following constellation can be installed for the three-phase grid connection of a small wind turbine system:Wind turbine (10 kW)


3 x Windy Boy 2500 or3 x Windy Boy 2800i or3 x Windy Boy 3000 or3 x Windy Boy 5000 A or3 x Windy Boy 6000 A

Small wind turbine system Windy Boy1 x wind turbine with 10 kW3 x WBP Box 5003 x load resistor


1 x wind turbine with 10 kW2 x WBP Box 6002 x load resistor

2 x Windy Boy 5000 A or2 x Windy Boy 6000 A

Small wind turbine system - system Windy Boy



Wind turbine (15 kW)



Small wind turbine system - system Windy Boy1 x wind turbine with 15 kW3 x WBP Box 6003 x load resistor

3 x Windy Boy 5000 A or3 x Windy Boy 6000 A


4 x Windy Boy 5000 A or3 - 4 x Windy Boy 6000 A


5 x Windy Boy 5000 A or4 - 5 x Windy Boy 6000 A

Technical Information Windy Boy Setting


5 Windy Boy SettingBecause the Windy Boy Protection Box represents an additional load on the wind turbine through the load resistor once a preset DC voltage is exceeded (see Section 3.1), the Windy Boy must be set accordingly. You can achieve the best performance when the Windy Boy loads the wind turbine with maximum capacity before the switching voltage is reached.For this purpose, two parameters must be adjusted on the Windy Boy:

• UDCWindMax• Pmax

Application with WBP Box 400



Thermal destruction of the generatorWhen the voltage UDCWindMax is set, Pmax must not exceed the maximum value recommended by the wind turbine manufacturer. Too high Pmax values lead to excessive generator currents and destroy the generator. In this respect, please consult your wind turbine manufacturer and read the respective documentation of the wind turbine.

UDCWindMax: Set this value below 360 V.Pmax: Set the capacity recommended by the wind turbine manufacturer which the generator

provides at approx. 360 VDC.





Windy Boy Protection Box - qrsrenewables.ie

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