Research On Single-phase Voltage Regulator With Controllable Phase And Amplitude

The development of interconnected network in electric power system is a trend for modern power system in country all over the world. However, in the wake of this development, electric network control system gets increasingly complicated. Thus, in order to meet the needs of power system, all kinds of control devices which are designed to adjust energy transfer of power system are developed, namely tapped transformer, parallel reactive power compensation, current limiting conductor, distributed series impedance, unified power flow controller, Synchronous static series compensator etc. Yet they are confined in their usage for their intrinsic defects and strict application conditions, in spite of their function in the control of energy transfer of power system. Recently, the proposal of concepts like VQS (virtual quadrature source), VRCPA (voltage regulator with controllable phase and amplitude), etc provides a new way for the design of electric network control system. Being capable of adjusting phase and amplitude of voltage independently and flexibly, VRCPA is potentially valuable. For it could be applied to the energy transfer of power system to enhance power transmission of electric network. Based on these concepts, this paper conducts a thorough research about the circuit structure and operation principle of single-phase(VRCPA) as well as their design. The circuit topology of single-phase(VRCPA) is comprised of pre-stage convertor and back-stage convertor. As for pre-stage convertor, it is made up of Buck type AC converter and the 3rd harmonic trap,while the back-stage convertor is consist of Boost type AC converter.First of all, this paper makes an analysis of the circuit structure of PWM Buck type AC converter and PWM Boost type AC converter. A thorough research about the circuit structure and operation principle of cascading PWM Buck-Boost AC converter is also included here. According to its operation principle, the paper introduces variable structure control strategy and conducts a simulation and experiment for it. What's more, the simulation and experiment have confirmed that cascading PWM Buck-Boost AC converter enjoys the following merits, such as pressure-boosting and pressure-reducing, good dynamic performance and low voltage stress, etc.Secondly, as cascading PWM Buck-Boost AC converter is not capable of adjusting phase voltage. Thus the paper introduces concept VQS which means to add an AC component with double frequency to the duty ratio of Buck type AC converter. However, in addition to the fundamental voltage with phase shift, it also produces the 3rd harmonic voltage. To get rid of the 3rd harmonic voltage, the paper comes up with the 3rd harmonic trap which ends up with fundamental voltage with phase shift. Back-stage convertor is used to adjust voltage amplitude. A study about the operation principle of single-phase(VRCPA) has been carried out through simulation.DSP software has been employed to design the process of signal control of Buck type AC converter. What's more, the design of the 3rd harmonic trap is covered in this paper. A prototype with the same operation principle as single-phase(VRCPA) is designed and the finding and data of experiment show that single phase and amplitude voltage regulator have the function of adjusting phase and voltage amplitude.Finally, the paper gives a general introduction of triphase and amplitude voltage regulator. The 3rd harmonic voltage could be cancelled out because of symmetric relation of triphase, thus making the 3rd harmonic trap circuit unnecessary. So it's promising and valuable to apply voltage regulator with controllable phase and amplitude to three-phase supply.