| The three-phase voltage source inverter circuit is widely used in various industries due to its high efficiency and stability.However,the inevitable harmonic components in the inverter system have significant negative effects,such as causing electromagnetic interference and vibration,stimulating audible electromagnetic noise and increasing system losses.Therefore,with the increasing awareness of energy conservation and environmental protection,people are paying more attention to reducing inverter noise,eliminating harmonic pollution,and improving inverter performance.Space Vector Pulse Width Modulation(SVPWM)technology has become an important control algorithm for three-phase voltage source inverters due to its simple control,convenient digital implementation and high utilization of DC voltage.Although the existing SVPWM technology can reduce some harmonic components of the inverter output signal,there are still three significant harmonic components in the inverter process.The first type is the low-frequency signal component near the frequency of the modulated wave,which is mainly affected by the dead-time effect and the control method of the overmodulation region.The second one is the high-frequency signal component at the switching frequency and its doubling frequency.The third one is the high-frequency component of the edge frequency signal near the switching frequency and its doubling frequency.The latter two types are mainly affected by the solidification of the switching frequency of the SVPWM algorithm.Therefore,weakening or eliminating the harmonic components of the SVPWM algorithm in three-phase voltage source inverter circuits is a key issue in the field of power electronics research,which is of great value in research and practice.Firstly,in order to reduce the dead-time effect of the SVPWM algorithm in three-phase voltage source inverter circuits and reduce low-frequency harmonics of the inverter,a segmented compensation strategy for the dead-time effect of SVPWM within the full load impedance angle range is proposed in this dissertation,targeting the most common form of resistive and inductive load in three-phase voltage source inverter circuits.The relatively accurate dead-time effect time compensation method was used to make the segmented compensation strategies suitable for the dead-time effect laws in the impedance angle ranges of [0°,30°] and [30°,90°].The strategy compensates for the limitations of traditional dead-time effect time compensation methods that mostly analyze resistive load schemes.The conversion relationship between power factor and load impedance angle is used to determine the current polarity within the six sectors,avoiding the detection error generated by traditional schemes when detecting near the current zero crossing point.The strategy can compensate for over 7% of the vector amplitude lost due to dead-time effects.Compared to traditional dead-time compensation schemes,the region 2 dead-time compensation strategy proposed in this dissertation can further reduce the total harmonic distortion(THD)of the inverter output signal by more than 10%.The strategy is applicable to the linear modulation region of the SVPWM algorithm.The compensation effect decreases due to vector boundary limitations in the overmodulation region I,while there is no compensation effect in the overmodulation region II.Secondly,the SVPWM overmodulation strategy adopted to improve the utilization rate of DC voltage generates relatively less low-frequency harmonic content in the overmodulation region I,while the low-frequency harmonic impact in the overmodulation region II is relatively large.Therefore,the SVPWM overmodulation region II rotation angle optimization control strategy based on chaotic ant colony algorithm is proposed in this dissertation.The advantages of chaotic ant colony algorithm in path optimization are applied to the control process of overmodulation region II rotation angle transformation in SVPWM technology.Through data modeling of the iterative process of chaotic ant colony algorithm,the optimal scheme of gradually changing the rotation angle between sectors to gradually change the output voltage vector amplitude is finally determined.In addition,the transformation formula for the optimized rotation angle within six sectors,as well as the relationship between the holding angle and modulation ratio have been derived,both of which are relatively simple and suitable for online calculation.This control strategy features stable and reliable operation,and smooth transition of the electrical signal waveform within the algorithm control range.To conclude,compared to the traditional control scheme with a large step in the rotation angle of the overmodulation region II,adoption of this strategy reduces the total harmonic distortion of the algorithm by more than 10%,and has a significant suppression effect on low-frequency harmonic components.Thirdly,the switching frequency of the basic control strategy of SVPWM algorithm is fixed and unchanging,resulting in significant high-frequency harmonic components near the switching frequency and its doubling frequency.Based on the basic principle of random switching frequency SVPWM control,a frequency optimized distribution random switching frequency SVPWM(FORSF-SVPWM)control strategy is proposed.The chaotic ant colony algorithm is used to determine the optimal scheme for the distribution of switching frequency in FORSF-SVPWM.Through theoretical derivation and experimental proof,the frequency samples formed by the sigmoid function curve within the switching frequency range—where the frequency samples on both sides are more distributed than in the middle region—can make the energy originally concentrated on the switching frequency and its doubling frequency more evenly distributed throughout the entire frequency range.Compared to the traditional Random Switching Frequency SVPWM(RSF-SVPWM)strategy with approximately linear and uniformly distributed frequencies,the FORSF-SVPWM strategy further reduces the amplitude of high-frequency harmonics by about 20%,effectively suppressing high-frequency noise and conductive electromagnetic interference in switching circuits.The strategy is suitable for linear modulation and over modulation regions of SVPWM technology.Finally,combining the control characteristics and applicable characteristics of three optimization strategies,namely dead-time effect segmented compensation,overmodulation region II control,and FORSF-SVPWM,an overall optimization scheme for harmonic suppression of the SVPWM algorithm within the full modulation range is formed.The full modulation range includes three regions: linear modulation region,overmodulation region I and overmodulation region II.The traditional three-phase voltage source inverter circuit SVPWM control algorithm and the overall optimization strategy for each modulation region proposed in this dissertation are compared and analyzed through simulation and experiments to verify the effectiveness of the optimization strategy in improving the performance of the inverter system.The overall optimization strategy is based on the SVPWM algorithm,and there is no need to change the topology of the inverter system circuit or add additional hardware equipment at any stage.Above all,the overall optimization strategy improves the harmonic suppression performance of the SVPWM algorithm through software optimization,which has important practical value and significance for improving the output performance of the inverter system. |
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