考虑漏感频变特性的三相立体卷铁心变压器建模及分析

Modeling and Analysis of 3D Wound Core Transformer Considering Frequency-Dependent Characteristics of Leakage Inductance

针对一种宽输入电压范围双向逆变电源,可采用磁集成方法提高其功率密度。与传统三相平面叠铁心变压器相比,立体卷铁心变压器具有磁路对称、重量轻等优势,该文拟开展PWM非正弦激励下考虑漏感频变特性的立体卷铁心变压器建模相关研究。首先,基于Foster频变磁阻模型,提出一种考虑漏感频变特性的立体卷铁心变压器模型,通过全局优化算法计算模型参数;其次,针对级联H桥组合式DC-AC拓扑的典型工作点,分析了PWM非正弦激励的谐波特征,重点关注不同H桥之间各次谐波的相对相位关系,给出简化等效电路;最后搭建逆变电源试验平台,开展了稳态和动态试验,验证了模型的准确性。

For a bidirectional inverter power supply with a wide input voltage range,the magnetic integration method can be used to increase the power density.Magnetic integration is used in two aspects:①core magnetic circuit integration;②filter inductor integration to isolate transformer leakage inductance.Compared with the traditional three-phase planar laminated core transformer,the 3D wound core transformer has the advantages of a symmetrical magnetic circuit and light weight.Due to the rich harmonic of PWM excitation,the frequencydependent characteristics of the leakage inductance of the 3D wound core transformer need to be considered.This article intends to carry out related research on the modeling of the 3D wound core transformer considering the frequency-dependent characteristic of the leakage inductance under PWM non-sinusoidal excitation.First,according to the principle of electromagnetic correspondence,the frequency-dependent leakage inductance in the circuit model was converted to the corresponding frequency-dependent reluctance in the magnetic circuit model.Based on the Foster frequency-dependent reluctance model,a 3D wound core transformer model considering the frequency-dependent characteristic of leakage inductance was proposed,and the model parameters were calculated by a global optimization algorithm.Secondly,according to the cascaded H-bridge combined DC-AC topology,the harmonic characteristics of PWM non-sinusoidal excitation were analyzed,focusing on the relative phase relationship of the harmonics between different H-bridges.The two transformers were triangularly connected in series on the secondary side,and the various harmonic components between different H-bridges on the primary side could be divided into four categories:positive sequence,negative sequence,zero sequence(one and two groups can cancel),and zero sequence(one and two groups cannot cancel).The dead zone led to a slight reduction of fundamental amplitude and the harmonic amplitude of the multiplier switching-frequency sideband under the PWM voltage excitation.Under load conditions,the 150Hz zero-sequence component caused by the dead zone generated the corresponding harmonic currents in the primary and secondary windings.Since the impedance at 150Hz excitation was small(mainly the leakage inductance of the primary and secondary windings),a significant zero-sequence current component would be generated.Under no-load conditions,the switching current was small,and the anti-parallel diode renewed,so the switching shutdown time was extended,the dead-zone effect could be ignored,and transformer winding didn’t contain 150Hz harmonic current components.Finally,an inverter power experimental platform was built,and steady-state and dynamic experiments were carried out to verify the accuracy of the model.Under the no-load steady-state condition and load steady-state condition of the inverter power supply,compared with the simulation results of the fixed leakage inductance magnetic circuit model,the fundamental frequency component of the primary current of the frequency-dependent leakage inductance magnetic circuit model had the same amplitude,and the simulation results of the main harmonic components of the multiplier switching-frequency sideband had higher accuracy.Under dynamic conditions,the relative error of the transient peak value of the primary current between the frequency-dependent leakage inductance magnetic circuit model and the experiment was 5.96%,which verified the accuracy of the frequencydependent leakage inductance magnetic circuit model under dynamic conditions.The frequency-dependent leakage inductance magnetic circuit model can be used to analyze the transient operating characteristics of the 3D wound core transformer under PWM non-sinusoidal excitation,and provide technical support for the application of the 3D wound core transformer in the field of power electronic conversion.