Study On Fixd Frequency Technology Of Active Power Filter Hysteresis Current Control Based On Space Voltage Vector

Active Filter(Active Power Filter, APF) is an important tool of harmonic pollution governance and green power grid construction, it’s performance depends particularly on the design and optimization of active power filter current control method. Hysteresis current control with excellent current control accuracy and dynamic response speed, is currently the focus of current control method study. Especially the constant frequency hysteresis current control method overcomes the shortcomings of the switching frequency fluctuations, has increasingly become the main development and research direction of hysteresis current control method. Meanwhile, the hysteresis current control and space voltage vector control technology research and development is also very rapidly, but for a long time, combination of hysteresis control and space vector control technology does not completely solve the three-phase interfere with each other, fixed-frequency control and other issues except to improve the accuracy. Based on the above analysis, on the basis of absorption of existing research results, look at the forefront of technological development, this paper made a thorough study of the theory and optimization improvementsfor on fixed-frequency hysteretic control technology and space vector control technology, not only in the control strategy absorb the advantages of the space vector control, while maintaining the advantages of high precision and fast response of hysteretic control. This paper made a study of the following aspects:1. This paper made a thorough study and analysis of fixed frequency hysteresis current control basic theory. Described the space vector theory and harmonic detection method based on instantaneous reactive power theory, expounded the basic idea of the fixed-frequency control method, and focused on a new phase-to-phase current decoupling control method.2. For three-phase three-wire active filter, combined with the optimal space vector pulse width modulation(SVPWM) technique to study the optimization of fixed-frequency current hysteresis control. This paper proposed a fixed-frequency control method base on space voltage vector, This method linearly predict next hysteresis width according to the previous switching cycles, and using a reference clock signal to adjust switching phase, then achieved the constant frequency hysteresis current control, further by calculating and analysing the current error of the two different continuous and discontinuous SVPWM modulation, the optimal discontinuous SVPWM modulation is proposed and applied to above fixed-frequency control method. error current is further reduced by alternately using two different discontinuous SVPWM modulation. Finally, use PSCAD / EMTDC power transient simulation software to verify, the results show the effectiveness of this method.3. Research on the constant frequency hysteresis control method of three-phase four-wire active power filter. A new fixed-frequency control method of four-leg APF based on space voltage vector is preposed, in this method, the three-dimensional space voltage vector was divided into four equal parallelepipeds, each parallelepiped on behalf of a group of phase current control object. A set of external hysteresis comparator was used to quickly determine the reference voltage region, then using methods mentioned in 2 to adjust the hysteresis width and error current phase, fixed frequency hysteresis control of three-phase four-wire APF can be achieved. Finally, use PSCAD / EMTDC power transient simulation software to verify, the results show the effectiveness of this method4. Study on a new fixed-frequency hysteresis current control which is suitable for three-level active power filter. Firstly analyse the topology and voltage vector space of Three-level APF, then take the single-phase three-level APF as an example, the basic method of realizing constant frequency hysteresis control for three level APF is studied. Based on the voltage vector space characteristic and current control equation of three level APF, the reference voltage vector is divided into 12 parallel quadrilateral regions, and a new method of constant frequency hysteresis control strategy and the new hysteresis controller are proposed. Combined two level active power filter with fixed frequency technique, the three level APF constant frequency hysteresis current control is realized. t At last, the results show the validity of the method by using PSCAD/EMTDC power transient simulation software.