DCM单桥臂集成Boost逆变器用PFM+SPWM混合调制策略

PFM+SPWM Hybrid Modulation Scheme for DCM Single-leg-integrated Boost Inverter

传统脉冲宽度调制(pulse width modulation,PWM)+正弦脉冲宽度调制(sinusoidal PWM,SPWM)混合调制下,电流断续模式单桥臂集成Boost逆变器在负载功率大范围变化时会产生过调制问题,导致输出波形畸变。采用恒定占空比且变输出功率的改进混合调制策略可避免上述问题,但无法应用于独立逆变、光伏并网等场合。为此,文章提出一种脉冲频率调制(pulse frequency modulation,PFM)+SPWM混合调制策略,使升压桥臂工作在PFM方式,逆变桥臂工作在SPWM方式。该调制策略不改变输出功率和升压桥臂的占空比,通过变频控制实现直流母线电压调节,可以避免负载大范围变化时输出波形产生畸变,且可以应用于输出功率不可调的场合,具有更强实用性。所提混合调制策略的可行性通过一台500W的原理样机得到仿真和实验验证。

Under the traditional pulse width modulation(PWM)+sinusoidal pulse width modulation(SPWM)hybrid modulation scheme,the DCM single-leg-integrated Boost inverter will confront over-modulation problem when the load changes in wide range,leading to the distorted output waveform.By keeping the boost-leg duty cycle constant and regulating load power can address this issue.However,it is not suitable for standalone inverters and photovoltaic grid-connected systems.Therefore,a pulse-frequency-modulation(PFM)+SPWM hybrid modulation scheme is proposed in this paper.Under the proposed scheme,the boost-leg of the inverter works in PFM while the other leg works in SPWM.Since the dc-link voltage is controlled by frequency,instead of output power or duty cycle,the inverter can also avoid over-modulation for wide load range.Besides,the proposed scheme can be applied in occasions where the load power is non-adjustable,which is more practical in comparison with the traditional one.The feasibility of the proposed hybrid modulation is verified by simulation and experiment through a 500W prototype.