Two stage single phase inverter is widely used in low voltage DC power supply system. This article firstly introduces the classification of the two-stage type inverter topology structure, and compares the advantages and disadvantages of the commonly used DC/DC converter topology and DC/AC inverter topology, and ultimately in this paper boost circuit is used as the former stage of the studied two-stage inverter and the single-phase full bridge inverter circuit is used as the after stage of the studied two-stage inverter. The former stage Boost circuit is used to achieve the voltage matching between the input and output of the inverter, and the full bridge inverter circuit is used for DC to AC conversion and power supply to the load. Based on the outstanding advantages of double loop control and digital control technology, the average current control which is achieved by DSP is used to the control of the studied two stage inverter system.The output voltage and current of two stage inverter system are alternating signal, which results that the output instantaneous power not only contains the DC component but also contains the pulse power whose frequency is 2 times as much as the output voltage, and the power input to the system is the DC power, which results the imbalance between the input power and the output power. The intermediate DC link capacitor is used as the decoupling capacitor of the pre and post stages of the two stage inverter, which absorbs the pulse power of the 2 harmonic in the system, which makes the voltage of the bus capacitor contain two times of low frequency voltage ripple. The low frequency ripple voltage will cause bus capacitor heating thereby endangering the operating life of the bus capacitor, will lead to the output voltage of two stage inverter clipping and distortion, will slso shorten the life of the battery, fuel cell, photovoltaic cells, etc, which are used as the DC input voltage source. In order to solve the problem caused by low frequency voltage ripple of the DC bus capacitor, this paper presents 3 kinds of suppression methods: changing the controller parameters, injecting two times of harmonics and output power feed forward. In order to verify the correctness and effectiveness of the proposed method, a 500 W two stage inverter is built in this paper. The experimental results verify the correctness and effectiveness of the proposed method. |