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The presence of distributed generators (DGs) with high penetration poses new challenges in the management and operation of electrical grids. Due to the local character of DGs, they could in principle be used in emergency situations to prevent a voltage instability event of the grid. In this paper, a certain method is proposed to coordinate the operation of virtual power plant (VPP) and conventional voltage regulation device to improve the static voltage stability of distribution network with the multi-agent framework. The concept and the general framework of this coordinated control system is introduced, and the voltage instable nodes are determined based on the voltage instability indicator. The voltage coordinated control model of the distribution system is established according to the multi-agent consistency control theory and the coordinated controllers for agents are designed by solving a problem with bilinear matrix inequality constraints. The suggested method is implemented on an IEEE 33 nodes test system and the simulation results show its efficiency and validity.

With the increasing of direct current (DC) transmission capacity, high-voltage DC (HVDC) location has become more and more intensive, and commutation failure has become increasingly prominent in multi-infeed DC (MIDC） transmission systems. To reduce the probability of commutation failure in MIDC systems, this study first analyses the fundamental causes of simultaneous or successive commutation failure, and puts forward the coordinated control strategy of voltage compensation variable slope voltage dependent current order limit, which takes the advantage of the DC current characteristics while fault occurs, and then proposes the influence factors and determination method of compensation coefficient K. Meanwhile add the switch function of K to compensate voltage according to the severity of the fault. Finally, built the actual system using PSCAD/EMTDC, simulation results show that the control strategy can effectively reduce the probability of commutation failure in MIDC transmission systems, and makes all DC systems recovery orderly after fault, meanwhile ensure the good recovery performance which can greatly improve the safety and reliability in MIDC transmission systems.

Many of papers refers to study of application for FACTS. Especially for using reactive compensators for 500KV power system in order to increase the static voltage stability margin and transient stability enhancement have considered. However the selection of suitable Var source (STATCOM or SVC) also need to be considered. The purpose of this paper is to solve the above problems in order to suggest a olution of the appropriate shunt compensator for a reality 500KV power system. All the simulations for the above work have been carried out using MATLAB-SIMULINK environment.

In the application of the traditional selective harmonic elimination technique, the lowest un-eliminated harmonic and the total harmonic distortion factor are obviously enlarged usually, which would do great harm to the power system. In order to solve the problem, this paper presented an improved harmonic elimination technique. In this new technique, a new circuit topology is proposed and only a small additional direct current source is added. In the time of eliminating the selected harmonics just like the traditional SHE-PWM technique, the system total harmonic distortion factor will reduce greatly, and the switching frequency in the circuit is only half of the traditional SHE-PWM technique, so the system performs better and the latter filter circuit could be of small size. In the analysis, it is clear that the traditional selective harmonic elimination is only a special example of the improved harmonic elimination technique, so the improved harmonic control technique will be more flexible and have better behavior than the traditional selective harmonic technique. In the end, the Fourier analysis in an example validates the feasibility of the improved harmonic elimination technique.

A new topology of hybrid power filter is proposed in this paper, which consists of a C-type filter and an active filter. The application of C-type filter not only reduces the rating of active filter but also prevents the resonance occurring significantly when proper parameters are used. The Iterative Learning Control (ILC) method is applied to the realization of harmonic compensation. In this paper, both the topology and the control method are discussed. Experimental results based on the proposed topology and control method are presented.

Lots of structures of hybrid power filter are produced consisting of tuned filter and active filter. It can reduce the rating of active filter and cost of the harmonic compensators, and also can improve the compensation performance compare to the passive and active filter using alone by preventing the resonance occurring. However, the resonance still may occur under some condition. A new hybrid power filter by employing an active filter and C-type filter is proposed in this paper, which can reduce the rating of this harmonic compensator, and moreover, the resonance can be suppressed reasonable. A simulation result will be presented in this paper, it proves that this kind of topology is effective on the harmonic compensation and elimination of resonance.

There is a bias between the estimated flux-orientation of a motor and its real flux-orientation in a vector control system. The paper presents the model of the permanent magnet linear synchronous motor (PMLSM) on the previous bias, and designs an experimental verification. The experiment removes the difficulty to measure a continuous force of the PMLSM's mover, and has advantages of easy operation and high precision. The tested results are used to control the PMLSM drive system for the maximum efficiency.

In this paper a method is proposed for compensating the dead-time in a synchronous rotating reference frame, which is suitable for general-purpose inverters. A simple and practical instantaneous harmonics current detecting method is introduced, which realizes a special filter based on DFT (discrete Fourier transform). The amplitude of this filter is 1 in first-harmonic frequency, the amplitude is 0 in other harmonic, and the phase of the filter is 0 in first-harmonic frequency. The filter can follow the fundamental wave in one period. Firstly the FIR filter is designed and its coefficients are worked out in this paper. Then the recursion of filtering algorithm is obtained according to the response character of the filter, and the calculation is thus greatly simplified. One result of the output only needs two multiplications and two additions. The theoretical analysis and simulation have shown that this filter not only takes advantages of digital filters in the accuracy, but also overcomes the bad dynamics performance

Based on digital signal processor (DSP) and intelligent module (IPM), this paper provides an example of vector control frequency conversion driving system, in which the fuzzy control algorithm is employed to improve control performance. The speed loop and current loop are employed in the frequency conversion system, where speed loop adopts automatic tuning control of fuzzy parameter, and the current loop adopts PI control.