| As an equipment of DC to AC power conversion, sine inverter takes on the broad market in both industry and folk applications. In the paper, a whole digital sine inverter is introduced, which is universal, programmable, intelligentized, and combinable.At the beginning, the basic topology and working theory of the inverting circuit is introduced. Following, the paper analyses and discusses the issues of hardware composing, parameter choice, controlling methods, and software implementing in the system. Finally, three 5KW sine inverters have been developed successfully and the auto-synchronous operation of the three single-phase inverters is implemented.A new controlling method to the auto-synchronous operation of the three single-phase inverters is issued in the paper, that is, three independent single-phase inverters can implement three-phase symmetrical AC output by being connected with each other, which can avoid the effect to the output of the inverter because of the asymmetric load. The system is composed of inverting subsystem and monitoring subsystem, which has the functions of keyboard monitoring and LCD display. Many kinds of faults auto-examining functions are provided in the system also, and its programmable design is adapted to many occasions. It is proved by experimenting that the circuit can solve the problem of three-phase asymmetric load effectively. The LCD display is designed as the mode of Chinese menu, which has the friendly interface and the functions of scrolling display and reverse display, etc. Using the MCU W77E58 as the key chip which has the dual serial ports, the standard RS-485 interface is used in the communication of the system. Meanwhile, all the parameters of the system state can be monitoring by LCD display and the computer.The paper also analyses the performance of the sample, furthermore, according as the developing trend of the inverting field, it reveals the improving and perfecting direction of the transformation from the sample to the product.
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