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Scientists in the United Arab Emirates have devised a new spatial vector pulse width modulation method that reportedly reduces switching losses and increases the efficiency of three-phase photovoltaic inverters. The proposed technique has been found to have higher efficiency, while providing lower common mode voltage, leakage current and total harmonic distortion compared to traditional pulse width modulation approaches.
Researchers at Khalifa University in the United Arab Emirates have developed a novel spatial vector pulse width modulation (SVPWM) technique to control switches and reduce switching losses in three-phase photovoltaic inverters.
The proposed approach aims to reduce the common mode voltage (CMV), which is generated by the switching operation of pulse width modulation (PWM) inverters and often causes bearing failures and electromagnetic interference (EMI) noise, and in some cases, ground leakage current, insulation failures and motor bearing failures.
In the paper “ An energy efficient control method of a photovoltaic system using a new three-phase inverter with a reduced common mode voltage” published in Heliyon , the group claims that the new SVPWM method effectively reduces inverter losses, minimizes the voltage time derivative (dv/dt) of the CMV, decreases the maximum peak value of the CMV, and simplifies the duty cycle calculation.
The proposed technique is intended for use in inverters with one 3-level leg, two 2-level legs, and 12 possible switching states: 10 active vectors and 2 zero vectors. “These additional voltage vectors help reduce the maximum peak value of the CMV as well as the dv/dt,” the scientists explain. “The new SVPWM generates the reference output voltage using only eight vectors.”
The performance of the new method was tested in a series of simulations and compared with that of other conventional pulse-width modulation (PWM) techniques. The scientists assumed a switching frequency of 2 kHz, a DC link voltage of 100 V, a load resistance of 11 O, a load inductance of 0.06 H, a parasitic photovoltaic capacitance of 500 nF, and a DC link capacitor of 4,700 µF.
The analysis showed that the maximum CMV value achieved by the new technique was up to 33.33% lower than the value achieved by conventional PWM methods. The new approach was also found to achieve 12.92% lower total losses, 0.65% higher efficiency, and required less complex and numerous mathematical calculations to calculate duty cycles and identify sectors compared to existing PWM approaches.The researchers also claimed that the new technique is capable of achieving balanced DC link voltage and higher performance with a higher modulation index compared to traditional PWM methodologies. |
