⚡🔧 MATLAB Simulation of Sliding Mode Control Strategy for Dynamic Voltage Restorer (DVR)
- lms editor
- 1 day ago
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A complete explanation of DVR operation, voltage sag mitigation, and sliding mode control implementation
Voltage disturbances such as sag, swell, and harmonics pose serious threats to sensitive loads like servers, computers, medical equipment, and industrial control systems. A short-duration fault in a distribution feeder can instantly drop the voltage, causing malfunction, interruption, or permanent damage.
To address this challenge, modern power systems use a power-electronics-based compensator known as the Dynamic Voltage Restorer (DVR). In this blog, we explore the MATLAB simulation of DVR controlled using a Sliding Mode Control (SMC) strategy and understand how it maintains power quality during faults and harmonic distortions.
🌐 What Is a Dynamic Voltage Restorer (DVR)?
A DVR is a series-connected custom power device designed to:
Inject a compensating voltage into the distribution feeder
Maintain load-side voltage at 1 per-unit even during disturbances
Protect sensitive loads from voltage sag/swell
Improve the overall power quality
It consists of:
A DC energy source
An IGBT-based voltage source converter
A series injection transformer
A fast switching control strategy
When a fault occurs in the distribution feeder, the DVR instantly injects the required compensating voltage to ensure uninterrupted supply to sensitive loads.
🏡 System Description – Domestic, Nonlinear & Sensitive Loads
The simulation model represents a typical distribution feeder with:
A domestic/nonlinear load
A sensitive load, such as computers or control equipment
A fault created between 0.1s and 0.3s
A harmonic injection between 0.4s and 0.5s
During these disturbances, the sensitive load must be protected by maintaining its voltage at 1 p.u. This is where the DVR and sliding mode control come into action.
⚙️ DVR Control Structure – Sliding Mode Control (SMC)
The DVR controller performs the following operations:
1. Voltage Measurement & Per-Unit Conversion
The load voltage is sensed and converted into per-unit values using the base voltage (415 V).
2. ABC → dq0 Transformation
To simplify control:
The three-phase voltages are transformed to dq0 components
Control is applied on Vd and Vq only
This helps in independent regulation of active and reactive voltage components.
3. Sliding Mode Control Loop
Sliding Mode Control is implemented on both Vd and Vq channels to generate robust reference voltages.
SMC advantages:
Highly robust against parameter variations
Fast dynamic response
Strong disturbance rejection
Ideal for non-linear power electronic systems
4. dq0 → ABC Conversion
The controlled dq0 voltages are transformed back to ABC to generate reference voltage signals.
5. Reference Comparison & Hysteresis Control
The reference voltage is compared with the measured load voltage.The hysteresis controller generates gate pulses for the DVR IGBT converter to inject the compensating voltage.
🔍 Simulation Results & Analysis
➡️ 1. Performance During Voltage Sag (0.1s to 0.3s)
A fault causes a deep sag in the distribution feeder across two phases.
Grid voltage dips significantly below 1 p.u.
But the load voltage remains perfectly maintained at 1 p.u.
DVR injects the exact required series voltage to compensate for the sag.
This verifies the effectiveness of the DVR under fault conditions.
➡️ 2. Post-Fault Restoration
After 0.3s, the fault is cleared.
Both grid and load voltages return to normal.
DVR stops injecting voltage since the system has stabilized.
This demonstrates seamless transition back to normal operation.
➡️ 3. Harmonics Mitigation (0.4s to 0.5s)
Harmonics are intentionally added to the grid voltage.
Grid voltage becomes distorted (non-sinusoidal).
DVR injects an opposite harmonic voltage to cancel out distortion.
As a result:
Load voltage remains purely sinusoidal
Maintained at 1 per-unit, even during harmonic disturbance
This confirms the DVR’s ability to improve power quality under non-ideal grid conditions.
🎯 Key Benefits of Sliding Mode Controlled DVR
Robust compensation under sag and harmonic conditions
Fast transient response
Stable performance during severe faults
Improved protection for sensitive loads
Effective voltage regulation in distribution networks
🏁 Conclusion
This MATLAB simulation successfully demonstrates how a Dynamic Voltage Restorer, controlled using a Sliding Mode Control strategy, efficiently mitigates voltage sag and harmonics in a distribution system.
By injecting the appropriate compensating voltage in real-time, the DVR ensures that sensitive loads always receive a stable 1 p.u. voltage, even during severe disturbances. With its robustness and nonlinear handling capability, SMC proves to be an excellent control method for DVR applications.
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