Current and Voltage Sources

SEE ALSO: Controlled Voltage & Current Sources

Introduction

The current and voltage sources represent a single or three-phase AC voltage source with a series or parallel RLC impedance. The value of at least one of the R, L and C elements must not be zero.

Icons and Diagrams of Current and Voltage Sources

Properties

Represent single or three-phase AC current or voltage sources with a series or parallel RLC impedance

Features

• The voltage source always has a series connected impedance.
• The current source always has a parallel connected impedance

Sources Implementation
In the network, the current and voltage sources are implemented as follows:

• The voltage source always has a series impedance. This impedance consists of series or parallel connected R, L, C elements The current source always has a parallel impedance. This impedance is made up of series or parallel connected R, L, C elements.
• The voltage source has only one network connector as it is always referenced to the ground. The current source injects a current from one bus to another, without any grounding.

Sources Implementation

Parameter Description
Figures 4 - 3 and 4 - 4, respectively, illustrate the control panel of a voltage source and of a current source. Most of the fields and controls are the same for both control panels.

General Parameters

RLC Connection = Series (series R, L, C) or parallel (parallel R, L, C) see Figure 4 - 2;
SI or pu units:

• SI: Specifies the values of the RLC elements, voltage, current or frequency in international units (ohm, henry, farad, volt, ampere and hertz);
• pu: Specifies the values of the RLC elements, voltage, current or frequency in pu;

Base values for conversion in pu:

• Base MVA: Base power per phase in MVA;
• Base volt: Base voltage phase to ground in kilovolt;
• Base Freq: Base frequency in hertz;
• R: Resistance value in ohms (or pu) for each phase (in order: a b c);
• L: Inductance value in henry (or pu) for each phase (in order: a b c);
• C: Capacitor value in farad (or pu) for each phase (in order: a b c);
• Frequency: Source frequency in hertz (or pu);
• Module: Peak value of the amplitude for the source voltage or current in volts (or pu) or amperes (or pu) for each phase;
• Note : For pu, you have to enter 1.4142 pu
• Angle: Angle of each phase in degrees. The value of the angles can be modified either by directly entering the numerical values in the appropriate fields or by adjusting the hands on the dial.
  The input of the angle varies as a function of the sequence selected in the “Source control” section.
• Note : The current source is always in positive sequence and, hence, it does not have a sequence selection button.

Here is how to input each phase sequence.

• 1 Direct or Inverse (positive or negative): In this mode, a constant differential of 120 degrees is maintained between the phases when the phase angle is changed by entering the value in the field or by adjusting the appropriate hand on the dial. All the fields are reset and all the hands are repositioned to maintain this 120 degrees differential. The only difference between the positive and negative sequences is that in the latter, the signs for phases b and c are inverted.
• 2 Zero (homopolar): Here, a, b and c are in phase. Their differential is zero. When a field is modified or a dial handle is set, the other two phases automatically take the same value and the same position.
• 3 Per phase. The “Per phase” mode allows users to define the same angle for the phases selected using a checkmark. The other phases are not involved. If many phases are selected, modifying a field or setting a dial handle for one phase automatically brings the other phases to the same value and position.

Source Control Source (Active/Inactive): To activate or deactivate the source.

• Starting mode (Slow/Fast): If “Fast”, the source is immediately activated or deactivated. Figure 4 - 5 (a) shows what happens when the source is activated in Fast mode. If “Slow”, when the source is activated, the amplitude of the source increases linearly from zero to the steady-state value. When the source is deactivate, the amplitude of the source decreases linearly from the steady-state value to zero. Figure 4 - 5 (b) shows the behavior of the source when it is activated in Slow mode.
• Sequence (voltage source only: Direct/Inverse/Zero/Per phase): Allows users to set the phases of the three-phase source as a sequence. The positive sequence sets the angles of phases a, b, c at 0, -120, 120 degrees. The Inverse sequence sets the angles of phases a, b, c at 0, 120, -120 degrees.The Zero sequence sets the angles of phases a, b, c at 0, 0, 0 degrees (See preceding paragraphs on angle input).

Control System (Waveform Generation)

• Origin: Origin of the signal for the voltage source: “Internal”, “External” and “Simulink” for a Simulink model.

Note: Please note that most source controls (amplitude, angle, etc.) are inoperative in external or Simulink mode. Simulink:

• Model name: Name of Simulink model implementing the wave generator;
• Model directory path: The full directory path where the model is saved;
• Execution time: Model estimated or measured execution time of the Simulink model.

Load Flow Parameters
(Voltage Source Only) These parameters can be used for the steady-state solution of the network.

Activation of voltage source (a): Fast mode, (b): Slow mode
List of Available Signals
At acquisition, the following signals are made available by the sensors: I (a, b, c)_label: Source current (A); VINT(a, b, c)_label: Source voltage (V). (voltage source only) (before the impedance);
• P_label: Active power (voltage source only) (instantaneous);
• Q_label: Reactive power (voltage source only) (instantaneous).