| Digital control of PWM (Pulse Width Modulation) inverter system becomes a popular research area in power electronic technology with the appearance of high performance power transistor and DSP controller. The application of cybernetics technology can upgrade the stability of the system's output voltage, improve the performance of the dynamic and the steady response, also make the products easily standardized and upgraded. To meet the trend of a digital, modulational, network, intellectual PWM inverter system, the dissertation focused on the research of its digital control key technology, and provides theory foundation and realization means for the system's supply design and development.(1)Digital PWM inverter system's application field and development trend have been researched. The theory and technique foundation have been deeply researched based on the digital PWM inverter system's waveform control, inverter control and system control argument. The paper explained the research background of the project and the project tasks undertaken by author.(2)To reserach digital single-phase PWM inverter, the main circuit was separated into inverter model and output filter model, and its mathematical model was built independently. The inverter model was equival to an amplifier. The LC parameters of the output filter model had been analysised and designed. To reserach digital three-phase PWM inverter, the mathematical models based on abc coordinate,αβcoordinate transformation, dqo coordinate transformation were built independently. The three-phase filter can be decoupled to two single-phase filters through coordinate transformations. So it's easy for three-phase inverter model introducing single-phase inverter study method. The simulation models of the digital single-phase and three-phase PWM inverter systems were found to make the system structure clear and convenient for the system control algorithm design..(3)To solve the problem of the performance and load adaptability of PWM inverter system being not satisfying, this paper researched several practical digital waveform control strategies. Through the controller arithmetic deducing and analysis, the controller realization method was put forward. And through the simulation research, its own characteristic was analyzed and compared to each other. In addition, the paper put forward neural network internal model control theory based on inverter waveform control arithmetic. The algorithm could effectively enhance the system dynamic or static performance and system load adaptability.(4)According to the single-phase inverter and the three-phase inverter, digital inverter control technology was studied on two categories of carrier modulation and space vector modulation. In the category of single-phase inverter, a pulse multiplied digital SPWM technique was put forward. And its waveform spectrum proved that the technique can obtain twice the harmonics frequency than the common SPWM technique can, under the same carrier frequency. Through introducing the concept of single-phase inverter"line voltage", a single-phase space vector PWM technique was studied and its DSP realization method was put forward. The research proved the equivalence between carrier PWM and space vector PWM in single-phase inverter. In the category of three-phase inverter, the theory of the three-phase carrier PWM and space vector PWM technology were studied and its DSP realization methods were put forward. This paper also further studied and compared the two PWM inverter control algorithms, and proved that they are equivalence in nature. The results proved that space vector PWM is a special kind of carrier PWM, the zero sequence signal is the connection with space vector PWM and carrier PWM.(5)For the inverter system control and function realization, the paper analysised and researched the phase lock algorithm based onμC/OS-II operation system. Take inverter power for example,μC/OS-II operation system was transplanted to microchip LF2407A and the system duty was divided and dispatched. A synchronous modulation algorithm and an asynchronous varying-Frequency modulation algorithm based on the inverter digital phase lock technique were put forward. These arithmetic effectively solved the impact problem of the system and loads in the EPS(Emergency Power Supply) bypass/inverter output switching, and also solved its quick start and fast-switching problem under the city power failure.(6)The digital PWM inverter control key technologies were using to develop power products, realize products promotion and enhance its performance. The paper explained the design innovation of digital EPS system by the control key technology algorithm's realization, core hardware module's development and software system's design of a 70kW digital three-phase EPS's design and application. The digital PWM inverter sysytem's control key technologies improved control precision, track speed and solved the EPS quick start and fast-switching problem. The EPS prototype completely met the standard requests and the anticipated design requirements. As 2010's new product, it has been invested market using. The research and development of digital PWM inverter system control key technology, waveform control strategies enhanced system dynamic and static responding characteristic, inverter waveform quality and load adaptability. Inverter control arithmetic solved inverter power control problem, simplified the control arithmetic and improved inverter efficiency. The phase lock algorithm solved the EPS bypass/inverter output switching impact problem and quick start and fast-switching problem.
|
PDF Full Text Request