BCVTB + EnergyPlus8.2 - unable to set constant value of solar radiance through the whole simulation

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I am using EnergyPlus and BCVTB to simulate nonlinear plant model for my Matlab MPC controller. For purpose of experiment i need to set direct and diffuse solar radiance to constant value through the whole simulation. I am using EMS ExternalInterfaces:Actuators defined in this way in idf file:

ExternalInterface:Actuator,

DirSolarRad,             !- Name
Environment,             !- Actuated Component Unique Name
Weather Data,            !- Actuated Component Type
Direct Solar,            !- Actuated Component Control Type
300;                     !- Optional Initial Value

ExternalInterface:Actuator,

DiffSolarRad,            !- Name
Environment,             !- Actuated Component Unique Name
Weather Data,            !- Actuated Component Type
Diffuse Solar,           !- Actuated Component Control Type
100;                     !- Optional Initial Value

In simulation (3 days long) i set those actuators to constant values (30, 10 W/m^2). When i read output variables (Site Diffuse Solar Radiation Rate per Area, Site Direct Solar Radiation Rate per Area) i get square wave (see attached plot), not (what i want) straight horizontal lines.
For some reason during significant amount of time those values are set to 0. I suppose there is some kind of availability schedule inside, but i can't find the exact reason of this behavior.

Does anyone have any ideas what causes this behavior and how can i make those value constant in time?