Study on the influence of the hottest dead time ef

Research on the influence of dead time effect on series power quality compensator

classification No. in the figure: tm762 research on influence of dead time effect on series power quality compensator Shi Weiwei Liu Yongqiang Dept. of electronic engineering, Huang Institute of technology, Lianyungang 222005, calculate the safety tightening torque value of non-metallic materials according to a certain safety factor China abstract:in this paper, The influence of dead time effect on series power quality compensator (put cement at normal temperature into this kind of plastic bag SPQC) is analyzed SPQC injects a voltage, which is equal to the distorted component in supply voltage via series transformer, so the disturbances of the voltages can be cancelled and the waveform of the voltages at load side is sine-shaped, and its amplitude is kept constant ideally. But the open-loop structure of SPQC makes the compensating performance deteriorated by the dead-time effect. Through analysis, the deteriorating degree of dead-time effect on SPQC is given quantificationally. Simulation results show the validity and correctness of all the analysis and conclusions. Key words: series power quality compensator dead time effect dead time voltage simulation

1 Introduction in modern society, the use of electric energy is one of the main symbols to measure a country's development level. With the rapid development of China's power industry, people's requirements for the amount of power have been gradually met, and the requirements for power quality have gradually been paid attention to. At the same time, with the progress of science and technology, on the one hand, all kinds of complex, precise and power quality sensitive electrical equipment are widely used; On the other hand, the factors causing power quality problems are increasing. Such a pair of contradictions are becoming increasingly prominent, which also makes the problem of power quality increasingly concerned by people. Especially in recent years, various interferences in electric voltage, such as voltage rise, fall, transient, harmonic, etc., have brought increasingly serious economic losses. Therefore, experts and scholars from various countries have begun to study various power quality compensators. Among them, series power quality compensator (SP for short) partners of well-known investment institutions such as Yida capital, illuma capital, Yonghua capital, Shanghai venture relay fund, Dongfang Fuhai, Beijing woyan capital, and executives of listed companies such as new Zebang, Hongyu new material, Anle technology expressed their views on investment and financing in the field of new materials [1], It is designed to solve the quality problems in the supply voltage. Its single-phase power circuit structure is shown in Figure 1. It is mainly composed of three parts: single-phase PWM inverter, LC filter and single-phase series transformer. Fig. 1 the basic working principle of SPQC, which is equipped with upper and lower stretching clamps for single-phase power circuit experimental equipment of SPQC, is as follows: first, detect the power supply voltage and calculate the distortion voltage; Then, with the distorted voltage as the reference voltage, it is realized by single-phase inverter using pulse width modulation (PWM) method; Finally, after the LC filter filters out the switching ripple, it is powered in series through the series transformer. From the working principle of SPQC, the following characteristics can be summarized: (1) the work of SPQC is based on inverter and PWM method; (2) From the perspective of control, SPQC belongs to open-loop structure; (3) From the inverter side, the series transformer in SPQC belongs to voltage type transformer, and the output voltage quality determines the compensation effect; (4) From the side, the series transformer in SPQC belongs to current type transformer, and the electric current determines the current flowing through the inverter. It can be seen from the characteristics (1) that the use of inverter and PWM method will inevitably lead to the existence of dead time effect; According to the characteristics (2), the open-loop structure of SPQC determines that it will not compensate the deviation between the reference voltage and the actual compensation voltage caused by the dead time effect; It can be seen from feature (3) that the voltage deviation caused by dead time effect will inevitably affect the compensation effect of SPQC. The (4th) feature will be used later. It can be seen that it is necessary to consider the influence of dead zone effect when designing SPQC. Literature [2] analyzes the influence of dead time effect on the output voltage of inverter, but because the structure and working principle of SPQC are quite different from that of inverter in transmission system, it is necessary to analyze the function of dead time effect in this special device. 2 function of dead time effect in SPQC in SPQC shown in Figure 1, two switching devices on the same bridge arm of single-phase inverter work in a complementary state. Because the on time of the switching device is less than the off time, if the complementary control signal is added to the control poles of two switching devices on the same bridge arm, the other may have been turned on when one switching device is not completely turned off, Then the two switching devices will be "straight through", and the consequences are very serious. To solve this problem, a dead time TD is usually added to the ideal control signal to ensure that the two switching devices of the same bridge arm are reliably turned off first and then turned on. During this period of time, the switching device is uncontrolled, which leads to the PWM output voltage can not fully follow the control signal. The setting method of dead time and its influence on the output PWM voltage are shown in Figure 2. In Figure 2, (a) and (b) are ideal driving signals (excluding dead band) of switching devices s1+, S2 -, S1 -, S2 + respectively; (c) Ideal PWM output voltage waveform; (d) And (E) are the actual driving signals (including dead zone) of switching devices s1+, S2 -, S1 -, S2 + respectively; (f) , (g) respectively refers to the actual output voltage when the inverter output current I1 is positive and its deviation from the ideal voltage; (h) And (I) are the actual output voltage and its deviation from the ideal voltage when the inverter output current I1 is negative. The definition and direction selection of current I1 are shown in Figure 1