Direct Power Control of a Three-Phase Inverter for Grid Input Current Shaping of a Single-Phase Diode Rectifier With a Small DC-Link Capacitor

This paper describes motor drive system fed by a single-phase diode rectifier without power factor correction (PFC) circuit or the input filter. The system considered in this paper consists of a single-phase diode rectifier, a three-phase inverter, and a small dc-link capacitor. Since dc-link capacitance of the proposed system is few microfarads, the shape of the grid input current is directly affected by electrical output power of the inverter. Using this aspect, two goals of the drive system, controlling torque of the motor and suppressing the grid input current harmonics, can be simultaneously achieved by controlling the output power of the inverter. The proposed method includes the motor current reference generation and the direct output power regulation by modifying the output voltage reference. With the proposed method, the harmonic components of the grid input current can be reduced under the limits of the regulation IEC61000-3-2, lower than those in the conventional method. Also, the cost and size of the inverter system can be significantly reduced by removing electrolytic dc-link capacitor and input filter from the system. The performance of the proposed shaping method was validated by the experimental results using the motor drive system with a 5μF film capacitor at dc link.