Closed loop of single phase AC voltage controller

A closed-loop single-phase AC voltage controller improves performance by automatically adjusting the output voltage

What Is Closed-Loop Control?

In a closed-loop system:

• Output is measured and compared to a reference (setpoint)
• An error signal is generated
• A controller (e.g., PI controller) adjusts the firing angle of SCRs or Triac to minimize the error

⚙️ System Components of Closed-Loop AC Voltage Controller

1. AC Source

• Single-phase sinusoidal supply (e.g., 230 V, 50 Hz)

2. Power Electronics

• Triac or 2 SCRs in anti-parallel
• Controls conduction angle → adjusts RMS output voltage

3. Load

• Resistive or RL load (e.g., heater, lamp, fan)

4. Voltage/Current Measurement

• Measures the actual RMS voltage or power across the load

5. RMS Calculator Block

• Computes output RMS voltage (can use built-in Simulink blocks or a custom RMS calculator)

6. Controller

• PI or PID controller
• Input: error between reference RMS voltage and measured RMS
• Output: firing angle (α) or control signal

7. Firing Angle to Pulse Generator

• Converts the firing angle to gate pulses for SCRs or Triac using zero-crossing detection + delay logic