摘要
中点钳位(NPC)型三电平逆变器存在直流侧电容中点电压失衡问题,传统虚拟空间矢量脉宽调制(VSVPWM)在中高调制度下中点调节能力较弱。为此,该文提出一种扇区重构型VSVPWM(SR-VSVPWM)。首先,通过引入等效中矢量并重构位于中高调制度的扇区,提高中高调制度下中点调节能力。其次,采用占空比调制法平滑开关切换。再次,对其多种调制度下的中点调节裕度进行分析,揭示影响其中点调节能力的因素。最后,通过Starsim硬件在环实验平台,验证所提方法的正确性和有效性,与传统VSVPWM单一小矢量调节相比,该方法有效地提高了中高调制度下中点偏移平衡速度与中点波动抑制能力。
As a typical multilevel inverter,a neutral point clamped(NPC)three-level inverter is suitable for large-capacity and high-voltage converters,which can effectively reduce current harmonic content.However,the NPC three-level inverter has the problem of neutral point voltage imbalance due to the structural characteristics of capacitive voltage division.The traditional virtual space-vector pulse width modulation(VSVPWM)has limited ability to suppress neutral point voltage fluctuation.Correcting its offset is challenging,especially in the medium and high modulation depths.Therefore,this paper proposes a sector reconfiguration VSVPWM.By introducing equivalent medium vectors and reconstructing sectors in medium and high modulation depths,small and medium vectors can fully participate in neutral point balance adjustment while retaining fixed sector division.This method can effectively suppress the neutral point voltage fluctuation and accelerate the recovery of the neutral point offset.There is only one balance coefficient for each fixed sector,which is easy to implement.Firstly,the equivalent relationship between a large vector and a medium vector is analyzed.An equivalent medium vector with constant amplitude is then constructed.The equivalent medium vector can participate in the neutral point balance by adjusting the proportion of medium and large vectors.After that,a virtual vector group,including equivalent medium vectors,is constructed.Furthermore,an equivalent medium vector VSVPWM(EMV-VSVPWM)is proposed,which improves the neutral point adjustment ability in the sector with a medium vector.Secondly,the level of modulation depth is divided based on the operational sector position,and the neutral point margin of the EMV-VSVPWM strategy depths is analyzed in one modulation period.It is found that the regions with weaker capacity of neutral point balance exist in high modulation depth.Therefore,a sector reconstruction VSVPWM(SR-VSVPWM)is then designed.The sector boundary and vector selection boundary in the medium and high modulation depths are separated to increase the proportion of small and medium vectors in such regions,which can enhance the neutral point adjustment margin.Furthermore,the neutral point balance coefficient of small and medium vectors is unified to reduce the computational complexity.Meanwhile,the vector sequence is optimized according to the principle of constant switching state,and the switching loss is reduced.The initial neutral point voltage offset and modulation depth experiments are carried out on a hardware experimental platform in the loop.The results indicate that the SR-VSVPWM strategy can achieve the fast balance of the middle point in pure resistor load and resistor-inductance load conditions.Compared with the traditional VSVPWM single small vector adjustment,the neutral point voltage offset is eliminated,and the balance time in the high modulation depth is reduced by about 46%.In addition,the current harmonics are also reduced.When the experiment on variable modulation depth is considered,SR-VSVPWM still exhibits strong suppression of neutral point fluctuations and good current quality in high modulation depth.After the switching frequency is reduced to 5 kHz,the neutral point fluctuation level of SR-VSVPWM is 79.1%of the traditional VSVPWM.
作者
胡瀚林
赵咪
黄毅
闫海超
鲁敏
Hu Hanlin;Zhao Mi;Huang Yi;Yan Haichao;Lu Min(School of Mechanical and Electrical Engineering Shihezi University,Shihezi 832003 China)
出处
《电工技术学报》
北大核心
2025年第8期2573-2586,共14页
Transactions of China Electrotechnical Society
基金
国家自然科学基金地区科学基金项目(62363030)
新疆维吾尔自治区科学技术厅重大科技专项项目(2022A01004-3)资助。
关键词
中点钳位(NPC)型三电平逆变器
虚拟空间矢量脉宽调制
中点电压平衡
扇区重构
等效中矢量
Neutral point clamped(NPC)three-level inverter
virtual space vector pulse width modulation
neutral point voltage balance
sector reconstruction
equivalent medium vector
