Tian Cuihua

The Research of Inverter's Control based on Immune Genetic Algorithm

This paper evaluates immune genetic algorithms (IGA) as a new nonlinear technique for control of inverter. The so-called IGA strategy is characterized by its speediness, diversity, tolerance and memory. It is well suited for online microprocessor implementation. A special C program for the algorithm is compiled. And the dynamic experimental platform based on DSP was built. Simulation and experiment results show that the algorithm quickly converged to the good solution within 25th iterations, and the solutions fitness and switching loss are great improved compared with the traditional control strategies

A Novel Neutral Electromagnetic Hybrid Flexible Grounding Method in Distribution Networks

This paper proposes a flexible neutral grounding method based on electromagnetic hybrid Petersen coil (EHPC), which consists of a magnetically controlled reactor and an active power compensator (APC). Under normal conditions, the systems neutral point grounds through a reactor of high reactance. When a single line-to-earth fault occurs, the EHPC can be controlled flexibly to suppress the recovery voltage of faulty phase and to reduce the ground-fault current to almost zero. This paper expounds the two operating modes and corresponding characteristics, the measuring method of insulation parameters of the system (mainly including capacitance to earth and leakage resistance), and the full compensation principle for arc suppression based on the equivalent negative impedance of EHPC. This paper also proposes a compound control method of neutral-to-earth impedance based on neutral-point displacement voltage and a compensating method for the harmonic component of the ground-fault current. Compared to traditional grounding methods, this method can be fast and reliably make the residual current approach almost zero without arc reignition while greatly reducing the output capacity of APC and, thus, decreasing the cost of this device. Simulations and experiments verify the correctness of this measuring method and feasibility of this flexible grounding control strategy.

Fault Location in Resonant Grounded Network by Adaptive Control of Neutral-to-Earth Complex Impedance

This paper proposes a fault location method based on the adaptive control of neutral-to-earth complex impedance in a resonant grounded system, whose neutral point grounds are via an electromagnetic hybrid Petersen coil (EHPC). The EHPC can be equivalent to a parallel circuit of a negative resistance and an inductance, both of which can be adjusted. When a permanent single line-to-earth fault occurs, the ground-fault current will be compensated to almost zero, and the capacitance to earth and leakage resistance of system can be measured accurately for subsequent fault location. Then, the complex impedance of EHPC is adjusted, and the faulty feeder and its faulted section can be identified online based on the characteristics that the measurements of zero-sequence admittances of points along the faulty feeder change with the systems neutral-to-ground complex impedance. The detection criterion is certain and unique, without comparing all of the feeders. This paper also proposes an adaptive jitter adjustment and decoupling control of neutral-ground complex impedance by EHPC, which is adaptive to the grounding transient resistance and is repeatable, and can ensure that the magnitude of the zero-sequence parameter is large enough to be measured while without arc re-ignition, including in high impedance fault states. Simulations and experiments verified the feasibility of this fault location method and its control strategy.

Study on a New Injecting Hybrid Active Power Filter

According to commonly used hybrid avtive power filter, the injecting active power filter is introduced to reduce the capacidance as much as possible without taking first -harmonic voltage. This paper illustrates the working principle of hybrid and injecting active power filter and proves with experiment.