Research And Application Of UHVAC Frequency-tuned Resonant Test Power Supply

With the development of China's UHV AC Transmission Project and the improvement of UHV AC electrical equipments'localization, whether in the research of UHV AC Transmission technology, or in the insulation testing of UHV AC electrical equipments, the UHV AC Test Power Supplies are indispensable. Thus, research on UHV AC Test Power Supply has great significance, which would greatly promote the development of UHV AC power system of China and improve its operation stability. At present, the research on the theory of UHV AC Test Power Supply, key technology and its engineering application are few in our country.Based on the key technologies of UHV AC power transmission project of State Grid Corporation-UHV Frequency Tuned Resonant Test Power Supply (UHV-FTRTPS), this paper proposes a most completely theory, key technologies, equipment research and applications relying on UHV-FTRTPS. It takes theoretical study and engineering application of UHV-FTRTPS as the main line. It also studies the basic working principle, topology, design and production of the main structural components, control algorithms of UHV-FTRTPS and the field engineering application of UHV AC Transmission, etc.Based on the introduction of universal structures and basic resonant methods of UHV-FTRTPS, this paper gives the detail description of UHV-FTRTPS's basic principles and structure on the basis of analog amplifiers. This paper also makes further research on the subcircuits, technological features, working principle and key parameters selection of this type. This paper also gives the first description of the relationship between the size of UHV electrical equipment, the weight of the entire power supply and the capacitive reactive power of the load. In addition, the relationship between the quality factor of UHV's resonant circuit and the frequency's upper limits of UHV-FTRTPS's output voltage has also been proposed. It can be found that UHV-FTRTPS has a good performance when the frequency's upper and lower limits are 30Hz and 300Hz respectively. Combined with the characteristics of UHV-FTRTPS's circuits based on the analog amplifiers, deeply study on the amplitude and frequency control methods of voltage have been carried out. According to the proposed intelligent control algorithm, the output signal frequency can be had coarse tuning first, then had fine-tuning. The accuracy of frequency control is up to 0.1 Hz. Moreover, the fuzzy optimal nonlinear PI of voltage amplitude modulation was proposed in this paper. Fuzzy control was used in large deviation range to obtain better transient performance. While, optimal nonlinear PI control was used in small deviation range, to obtain better steady-state performance and overshoot suppression performance. The whole control algorithm has the fast response and robustness.With the development of power electronics technology, a variety of power switching devices are continuously available. This paper proposes a new UHV-FTRTPS based on Non-controllable rectifier and H-bridge inverter by applying present power electronic technology. This paper gives the basic principle and resonance Principle of this UHV-FTRTPS. Buffer circuit and output filter of high-power H-bridge inverter are optimum designed in this paper. On one hand, optimization objectives of buffer circuit has been set up, according to the ability that the buffer circuit suppresses IGBT's turn-off over-voltage, its own power loss and the investment of the devices, on the other hand, objective functions about the optimal design of output filter have been established based on the initial investment of high-power H-bridge inverter's output filter, output filter's output voltage, THD of current and the fundamental voltage drop of output filter. Fuzzy optimization method is used to solve the two multi-objective functions. Voltage self-tuning PI control method has been designed for the voltage amplitude control of UHV-FTRTPS. A novel phase-locked PI automatic frequency method was proposed for the frequency control of UHV-FTRTPS. The proposed phase-locked PI control method not only has smaller amount of calculation and is easy for engineering application, but also does not need frequency setting value.In order to ensure that the voltage and the current at input side of UHV's rectifier have same phase, eliminate UHV-FTRTPS's impact on the grid as much as possible, this paper proposes the topology of UHV-FTRTPS based on controllable PWM rectifier and H-bridge inverter. The source voltage estimation is presented in the PWM rectifier controller. This paper also presents the double closed loop control strategy, which takes resonant capacitor voltage as outer loop and output filter capacitor current as inner loop. The controlled variable of inner loop is a sine quantity, so the multi-mode recursive PID is used to eliminate steady-state error which generated by periodic changed signal. In order to get the best output signal waveforms of UHV-FTRTPS, the synchronized SPWM is used in 167-300Hz high frequency bands. Meanwhile in order to get best carrier ratio N and minimum apparent power filter of output filter, the value of carrier ratio N and the structure of output filter are combined. The SHEPWM is used to real-timely calculate the switching point in 30-167Hz low frequency bands. The low-order harmonics is weakened and transferred to the high-order harmonics, so the harmonics is easy to be filtered. At the same time, to improve filtering performance of LCL output filter, the virtual resistance has been introduced to its structure. The capacitor of output filter in series with a virtual resistance does not change the structure of output filter and add any hardware. The software control method is used to enhance the damping of output filter, so the high-order harmonics can be filtered easily.The different Topologies of UHV-FTRTPS studied in this paper have a common part-UHV generating circuit without partial discharge(PD), which is included intermediate excitation step-up transformer, high-voltage resonant reactors, high-voltage compensation reactors, high-voltage measured resonant capacitors and grading ring. Considering the fabrication and on-site needs, this paper gives the detailed parameters and production processes of every component and maintains every component have a small amount PD. At the same time, every component's type has been testified. The result shows that the design of every component is reasonable and meets the standards. According to the partial discharge test of TBEA Hengyang Transformer Factory's UHV transformer, this paper proposes a corresponding experiment program. Aiming at the 1100kV gas insulated switchgear(GIS) device's AC voltage withstand test of UHV AC experiment demonstration project Jingmen substation, this paper also proposes a corresponding experiment program. The proposed high-power UHV-FTRTPS based on analog amplifiers was used in the field experiment of UHV transformer and UHV GIS. The engineering application results show that this high-power UHV test power supply device can meet the requirements of UHV electrical equipment. In addition, this paper draws a conclusion about the key issues of UHV-FTRTPS's engineering applications and gives the solution of them.