Research On Unified Power Quality Controller (UPQC) And Its H_∞ Control Method

UPQC(Unified Power Quality Controller) is one of the most up-to-datedevelopment trends of Custom Power, which combines the functions of voltagecompensator, current compensator and energy storage device. Multiple power qualityregulation functions are implemented in UPQC simultaneously. UPQC is a moreeffective way to regulate the power quality of distribution system systematically andimprove the reliability of power supply than others. Therefore, UPQC is becoming anemphasis of related research. Combined the subject 'Fundamental Research on Flexibility Distribution System'(No.1999007904) which is supported by Doctoral Fund from National Ministry ofEducation, this thesis 'Research on Unified Power Quality Controller (UPQC) and ItsH∞ Control Method' is carried on profoundly. The main contributions are as follows: 1. Profound research on the working principle of UPQC with a typical topologycircuit is carried on and its multiple functions of power quality regulation are statedsystemically. According to the development of power electronics and the present state ofcustom application, an economical and practical topology structure of UPQC isintroduced. This can improve the ratio of performance to cost for power qualitycompensation device greatly. The voltage control of dc link in UPQC is achieved byusing Active Power Factor Correction (APFC) technology. The technology not onlyensures that the energy storage unit of UPQC is charged in high power factor, but alsoavoids that it causes harmonic pollution to distribution network. 2. Based on the physical essence of instantaneous power in classical circuit theory,a rapid and direct detecting method of voltage and current compensation signals that canbe used in UPQC is put forward, meanwhile, a rapid and practical formula to calculatesinusoid voltage amplitude is presented, and so the rapid and accurate detection ofmultiple compensation signals is implemented. The validity of this direct detectingmethod is testified. 3. A new optimal control method based on H∞ model matching technology aboutvoltage and current waveform tracking compensation for UPQC is put forward for thefirst time. This method not only establishes the firm theoretical basis for UPQCimproving the control precision of voltage and current waveform tracking compensation,but also provides a new research way for the development of waveform tracking controltechnology in other related fields. A rational simplified mathematical model of UPQCshunt unit and series unit is developed in addition. A set of specific H∞ optimalcontroller for UPQC voltage and current waveform tracking compensation is designed byusing this H∞ method, meanwhile, its order reducing is achieved successfully. Thecorrectness and advantage of this design method of the UPQC optimal controller basedon H∞ model matching technology which is proposed in this paper is testified by anumber of powerful simulation experiments. The design method based on H∞successfully eliminates the additional phase shift and amplitude attenuation of UPQCcompensation output which are caused by its filter link and series-parallel transformer,and assures that the closed-loop control system is internally stable. 4. By analyzing the radical reasons of coupling effect between UPQC series unitand shunt unit, a coordinated control strategy for UPQC series unit and shunt unit isproposed. Based on this strategy, by introducing corresponding voltage correct link -iii-Abstractdirectly to UPQC series unit and shunt unit respectively, by a suitable mode of PWM inaddition, the coupling effect between its series unit and shunt unit is eliminated fully.Therefore, the complex degree of the whole UPQC control system is simplified greatly,and the coordinated control between UPQC series unit and shunt unit is implementedsuccessfully. A number of powerful simulation experiments prove that UPQC using thiscontrol strategy can imp...