Novel Harmonic Suppression Methods And Relative Techniques

As the development of the technique, there are many methods to suppress the power harmonic. But till now, they do not match the expectation of the industrial consumer. For example, to decrease the cost, the high power rating consumers expect the adopted passive power filters can be rebuilt by a suitable active filter scheme. So the passive filter can work normally in any load condition and get a best reactive power benefit. In the ASD household appliances, the power supply with a diode bridge rectifier is being one of maximal harmonic sources in the civil power line. At present, the existed active power factor correction (PFC) technique has not been adopted willingly for it will increase the cost and decline the reliability of a product. An integrative power system is expected, which integrates a PFC circuit and a conventional inverter with high efficiency, good reliability and suitable cost. In this paper, some existed harmonic suppressing technique is analyzed and summarized. And some practical technique researches are put forward, including the following three aspects, â…  . Research on the series type active power filter (APF)'s filter performance and its control stabilityA series hybrid active power filter (SHAPF) is a good solution to rebuild a widely being used passive power filter. For the parameters of power system are time-variant and APF self is a high order control system. It is very difficult to analyze the stability of the whole system of SHAPF. At present, the related public papers mainly study the control performance of SHAPF qualitatively. However, it is not enough to optimize its parameters only on this qualitative analysis.In this paper, a new analysis method on the control of series type active power filter is put forward. It qualitatively analyzes the stability of the related power system, while quantitatively study the control on the active part of the APF. Four specific measures to improve the series type active power filter's stability are generalized as increasing the switching frequency of the inverter, compensating the harmonic voltage directly, increasing the positive harmonic resistance of the system and adopting the leading compensating strategy. A new leading compensating strategy is put forward to improve the stability of SHAPF and a 10kVA prototype is given to introduce the related engineering design process. Experimental results show that the performance of SHAPF is improved a lot when the new control is adopted. The author expects this new analysis method can guide the design of series type APF effectively. â…¡. Research on decreasing the power rating of SHAPF's active partIn all the active power filter topologies, the conventional SHAPF is most attractive strategy for a consumer to rebuild its passive power filter. The power rating of its active part can only be 5%~10% that of the load. However it is still over the consumer's expectation. It is very significative to decrease the power rating of the conventional SHAPF's active part.In this paper a novel SHAPF is put forward based on the studies on the basic performance of the conventional SHAPF and that of its improved one. A LC circuit resonating at the fundamental frequency is adopted by this SHAPF to suppress the high order harmonics in power line. And its active part only needsto restrict those lower order ones. So the capacity factor of the inverter's DC voltage can be improved a lotand the power rating of the active part decrease markedly, while its filter performance does not decline. Theresonant circuit also can simplify the designing of the series transformer and the inverter's carrier filter. Itmakes it more practical to rebuild the passive power filter widely used in the industrial consumer withSHAPF.IE. Research on improving the efficiency of the APF's inverter and a novel active power factor correctionThe power dissipation of the inverter is one of main reason to restrict the application of high power rating APF. So it is very necessary to cut down this power dissipation. And at the same time, a reliable, low-cost, low power loss and "green" power supply scheme for a ASD household equipment is being the aim of the manufacturer.In this paper, a novel power converter and its control method for implementing DC-AC, AC-DC-AC, and DC-DC power conversion is presented, which named as a natural soft-switch power converter (NSS-converter) with adjustable DC voltage. Based on a general topology, a new two level three-phase NSS-inverter is studied. The theoretical analysis and experimental results show it has the following four new features, which are boosting the output AC voltage effectively, decreasing the switching dissipation of the conventional inverter markedly, the auxiliary switch working as a full soft-switch and having high reliability for only three auxiliary devices are adopted and the soft-switching condition is independent.NSS- inverter's control overlaps that of the conventional one. To describe its some special characters, in this paper, the modulation depth of the output line voltage is defined based on that of the conventional phase voltage. A new SVPWM control is also introduce to decrease the current stress of the inverter. And they enrich the conventional PWM theory. Based on the analysis of the voltage and current characters, the basic design rules are given. A prototype is finished. And experimental results are presented to demonstrate the new features.A new two level three-phase inverter special for APF is also introduced. Theoretical and simulating results show its feasibility to improve the efficiency of APF. As An integrative power system example, a new AC-DC-AC topology based on NSS-converter technique is presented. Experimental results indicate it is very possible that the NSS-converter power supply scheme can satisfy the requirement of the ASD household industry.