Study On Control And Soft Start Of APF DC Side Voltage

With the development of the society,all kinds of power electronic equipment are widely used in industry and daily life.It brings us a lot of conveniences,but meanwhile introduces power quality problem such as the harmonic.As an effective means of harmonic control,the active power filter(APF)can effectively suppress harmonics and compensating reactive power.The stability of APF DC voltage directly affects the output harmonic and power loss of APF,in addition,the DC side voltage will have a great impact during APF grid start process,which will cause damage to the DC side capacitor and IGBT,and then the traditional PI control is no longer applicable.So this paper focuses on the APF DC voltage stability control and soft start.The main work of this paper is as follows:Firstly,the paper analyzes the relationship between DC side voltage reference set value,power loss and compensation ability.And for the grid voltage fluctuations so that the DC side of the voltage reference set value can not take into account the output of the APF harmonic power and power loss,the optimal selection scheme of DC voltage reference value is proposed to satisfy the requirement of compensation when the power loss is low.Secondly,the cause of DC side voltage fluctuation is analyzed from the view of energy conservation,and the principle of DC voltage fluctuation in different working states of APF is introduced.And the mathematical model of voltage and current double loop control system and the voltage control of DC side is established.On this basis,the fuzzy control method of DC voltage and the fuzzy controller design method and steps are introduced,and aiming at the defects of the existing fuzzy +PI composite control,the paper puts forward two kinds of improved fuzzy +PI type double channel control method,which has better stability,and the DC side voltage fluctuations is smaller in load changing case.On the basis of theoretical research,the parameters of the device are designed to meet the DC voltage stability.For the DC side voltage control problems during start-up of APF,the paper analyzes the necessity of adding soft start,and soft start resistance method is introduced.Meanwhile,the parameter selection method of soft start resistance and resistance control after resection of soft start is given.The soft start method of Boost circuit with bridge arm itself is analyzedFinally,simulation and experiments are carried out to verify the DC voltage control method and the soft start method.The results show that the proposed improved fuzzy +PI control has a good control effect,it can effectively suppress the DC side voltage fluctuation when the load changes,and the additional resistance soft start method achieves the small impact target for APF when grid-connected.