dynamic voltage restorer

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dynamic voltage restorer

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Dynamic Voltage Restorer (DVR) is a power electronic device designed to protect sensitive loads from voltage sags and swells in electrical distribution systems. Implemented within the SimPower Systems toolbox (or Simscape Electrical in newer MATLAB versions), a DVR compensates for disturbances by injecting corrective voltage in series with the supply to maintain load voltage stability.

### Key Functionalities in SimPower Systems Voltage Sag Detection – The DVR monitors the grid voltage continuously. When a sag (a sudden drop in voltage) is detected, the control system activates compensation. Inverter-Based Compensation – A voltage-source inverter (VSI) generates the required compensating voltage, synchronized with the grid waveform to ensure seamless correction. Energy Storage Integration – A DC storage element (like a capacitor or battery) supplies power during compensation, ensuring the DVR can inject the necessary voltage during disturbances. Control Strategy – Typically, a closed-loop control (e.g., PI or PR controllers) ensures fast and accurate voltage restoration, maintaining the load voltage within permissible limits.

### Output Analysis In simulation, the DVR’s effectiveness is observed through: Load Voltage Waveform – Should remain stable (~1 p.u.) despite grid-side sags. Injected Voltage Profile – Shows the compensating voltage added by the DVR to counteract the sag. Power Quality Metrics – THD (Total Harmonic Distortion) and transient response time indicate performance.

### Voltage Sag Removal Techniques DVRs commonly employ: Pre-sag Compensation – Restores voltage to its pre-fault magnitude and phase. In-phase Compensation – Adjusts only voltage magnitude without phase correction for simpler implementation. Energy Optimization Methods – Minimizes DC-link energy consumption during compensation.

By modeling in SimPower Systems, engineers can validate DVR designs for real-world power quality improvement.