blue'Log XM/XC
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Part 1: Setpoint determination

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Note

The content on this page refers only to the blue'Log XC combined with the Hybrid EMS licence.


The reactive power setpoint is the target value a plant should maintain to ensure grid stability and compliant operation. It is either communicated by the grid operator or calculated by the controller.

image-20260206-143516.png
Reactive power controller: setpoint determination

The controller determines the reactive power control setpoint based on the power control mode you select. You can use a setpoint command or a characteristic curve as a power control mode. The reactive power controller can further adapt the setpoint by applying a Setpoint filter and reactive power limitations at the grid connection point (GCP).

Setpoint command modes

The setpoint is either transmitted via an interface (analog input, digital input, Modbus) or entered manually in the user interface (fix).

cos φ fix

A fixed cos φ setpoint can be configured manually via the user interface.

cos φ AI

A cos φ setpoint can be externally set via analog inputs (AI).

cos φ DI

A cos φ setpoint can be externally set via digital inputs (DI).

cos φ Modbus

A cos φ setpoint can be externally set via Modbus.

Q fix

A fixed Q setpoint can be configured manually via the user interface.

Q AI

A Q setpoint can be externally set via analog inputs (AI). Additionally, a voltage limitation can be configured.

Q DI

A Q setpoint can be externally set via digital inputs (DI). Additionally, a voltage limitation can be configured.

Q Modbus

A Q setpoint can be externally set via Modbus. Additionally, a voltage limitation can be configured.

Characteristic curve control modes

The controller measures grid parameters and determines a corresponding setpoint autonomously.

cos φ(P)

A cos φ setpoint is determined based on measured active power P and the settings of the characteristic curve.

cos φ(P) Modbus

Similar to cos φ(P). Additionally, the characteristic curve settings can be sent via Modbus.

cos φ(V)

A cos φ setpoint is determined based on measured voltage V and the settings of the characteristic curve.

Q(P)

A Q setpoint is determined based on measured active power P and the settings of the characteristic curve.

Q(V)

A Q setpoint is determined based on measured voltage V and the settings of the characteristic curve.

Q(V) Modbus

Similar to Q(V). Additionally, the characteristic curve settings can be sent via Modbus.

Q(tan φ)

A Q setpoint is determined based on measured active power P and tan φ.

Q(V droop)

A Q setpoint is determined based on measured voltage V and the settings of the characteristic curve.

Configure the reactive power control mode

Prerequisites

Steps

  1. Go to Power Control > Reactive power.

  2. In the Control mode dropdown, select the desired control mode.

  3. Under image-20260113-105107.png Extended settings, adjust the settings for each mode.

The reactive power control mode is now configured.


Note

To switch between different control modes, you can enable the Method switch for reactive power control.

Reactive power limitation at grid connection point (GCP)

The controller can be configured with reactive power limits that shall not be exceeded at the grid connection point. This reduces overshoots during fast changes in network conditions.

Caution

The reactive power limits at the grid connection point are not guaranteed in open-loop mode, as no feedback value is considered. In open-loop, only the setpoint and thus also the control value sent to the plant are limited.

 

Configure reactive power limits under Power Control > Reactive Power > Power limitation at grid connection point (GCP).