Dynamic Voltage Restorer (DVR) for Power Quality Improvement - Electrical Engineering Guide
1. Introduction
A Dynamic Voltage Restorer (DVR) is a custom power device designed to improve voltage quality by injecting or absorbing voltage during sags, swells, or harmonics. It is crucial for protecting sensitive loads in industrial and commercial settings.
2. Objectives
• Improve power quality by compensating voltage sags and
swells.
• Design a DVR system using power electronics and control algorithms.
• Validate performance through simulation and prototype implementation.
3. System Overview
The DVR is installed in series with the load and uses voltage injection to maintain a constant voltage level. It operates during transient disturbances to ensure uninterrupted and stable operation of critical equipment.
4. Working Principle of DVR
DVR detects voltage anomalies in the supply and injects an appropriate compensating voltage in series with the load using a voltage source inverter (VSI). Energy is stored in a DC link or external battery to support this operation.
5. Components Required
• Voltage Source Inverter (VSI)
• DC energy storage (battery or capacitor)
• Series injection transformer
• Voltage and current sensors
• Microcontroller or Digital Signal Processor (DSP)
• PWM generation circuits
• Protection circuitry
6. Circuit and Control Block Diagram
Supply → Injection Transformer → Load
↑
VSI ← DC Link ← Control System
↑
Sensing and Feedback Loop
7. Power Electronics Involved
• VSI configured with IGBTs/MOSFETs
• High-frequency switching for PWM-based waveform generation
• Proper snubber circuits and filters to reduce harmonics
8. Control Strategies (PI, PWM, etc.)
• PI Controller for voltage regulation
• PWM for inverter switching
• Feedforward + feedback control for real-time compensation
9. Microcontroller/DSP Integration
Use of STM32/Arduino/DSP to implement:
• Sensor data acquisition
• Real-time control algorithms
• PWM signal generation
• Fault monitoring and system feedback
10. Simulation and Modeling (e.g., MATLAB/Simulink)
Simulate system response to sags and swells using Simulink models. Analyze THD, voltage profile, and compensation accuracy. Compare open-loop and closed-loop responses.
11. Implementation Methodology
1. Design circuit using simulation tools
2. Build hardware: inverter + transformer + sensors
3. Program control logic on MCU/DSP
4. Conduct lab testing with programmable power supply
5. Validate output with oscilloscope and load bank
12. Testing and Validation
Introduce disturbances and monitor DVR response time, compensation accuracy, and voltage waveform restoration. Validate effectiveness using THD and RMS measurements.
13. Advantages and Limitations
Advantages:
• Real-time correction of power quality issues
• Improves equipment reliability
Limitations:
• Cost and complexity
• Requires precise control and sensing
14. Applications
• Semiconductor manufacturing
• Hospitals and labs
• Automated industrial plants
• Data centers
15. Future Work
• Integration with smart grids
• Use of AI/ML for adaptive compensation
• Bidirectional power flow for energy recovery
• IoT monitoring
16. Conclusion
A Dynamic Voltage Restorer is an effective tool to improve power quality in sensitive applications. With advanced control and monitoring, it ensures reliable energy delivery under varying grid conditions.