Research On Modular Control Methods And Module Combination Technology For Multi-function AC-DC And DC-AC PWM Converter

Inverter power supplies and voltage-type PWM Rectifiers have a huge market demand and a wide range of applications. With the expansion of applications as well as high requirements of its performance, there have been new hot spots and cutting-edge technology problems waiting for us to study in-depth.Modularity is one of development trends of power inverters. The system, using standardized modules in series and parallel combinations of inverter system, has a short development cycle and is easy to reconstruction, easy maintenance, and high reliability. In this paper, the modular design of the inverter system is implemented as follows. First of all, single-phase inverter powers act as the basic unit of the module. Secondly, according to different applications and requirements, the universal standardized basic unit modules are combined together to construct the inverter system. Therefore, single-phase inverter power supply should have a variety of functions as:parallel operation, grid-connection run, the composition of any phase of a multiphase power system.It can work independently, but also be combined into the power system to meet user requirements through a simple external connection.This paper focuses on the single-phase inverter power supply modular design problems and at the same time, two of the special problems of the three-phase PWM rectifier is in-depth studied.The following innovative achievements is obtained:We proposed the power inverter controller design method in the virtual circuit structure mode.We built a new mathematical model of the object and propsed the architecture of the virtual circuit structure design. It is proved that this method can achieve virtual power inverter circuit structure design.We proposed the virtual resistance matching mode control scheme suitable for parallel power inverter.The simulation and experimental results show:the the virtual resistance matching modeis simple and effective in inverter parallel system.We proposed the virtual resistor matching mode control scheme suitable for parallel operation power inverter.The goals to equalize the power inverter current and inhibit the DC circulation as well as inhibit the output voltage of the DC offset are itegated into the same controller. And the controller is relatively simple, easy to implement.We proposed the virtual structured design program suitable for general-purpose inverter power module. This program achieves parallel running and grid running of inverters and takes into account the performance of stand-alone inverter and it makes output voltages of inverters have a good degree of sinusoidal at any load conditions.Under the unbalanced power grid voltage conditions, three-phase voltage source PWM rectifier would produce AC current and DC volts harmonics. In order to solve this problem, we proposed the solution to use two sets of PWM rectifier modules in parallel form tha the main rectifier generate positive sequence current and the auxiliary rectifiergenerate negativesequence current. Ensure the requirement that there is no AC component in the main and auxiliary rectifier output to the DC side of the instantaneous power, we derived the relationship of the positive and negative sequence current, positive and negative sequence grid voltage and the DC power. Accordingly design a system capable of harmonic suppression to the level of grid equilibrium condition.For zero-sequence circulation problems caused by parallel running of three-phase voltage-type PWM rectifier, we proposed integrated solutions to suppress zero-sequence circulation. The program can effectively inhibit circulation, at the same time avoid the zero-sequence voltage occurrence of competition issues between the recifier modules,In this paper, the simulation and experimental verification of the proposed program is conducted in-depth.