The influence of interconnection scheme with AC or DC link on the power grid dominant oscillation mode and the frequency response of generator excitation control system were studied. The impact on the power system stabilizer (PSS) parameters requirements was also researched. Based on the above study, the PSS applicability for the Northeast-China Power Grid was validated in theory. The dynamic stability of the Northeast-China Power Grid in typical operation schemes, as well as the PSS impact on power system stability, was analyzed. The results demonstrate that the PSS of the Northeast-China Power Grid can satisfy the operating requirements for the DC link interconnecting North-China Power System.
The inductance and the flux linkage excited by the permanent magnet (PM) are largely influenced by the saturation of permanent magnet synchronous motor (PMSM), and the air gap flux excited by the PM often contains large amount of space harmonics. However, the traditional linear mathematic model of PMSM cannot reflect the effects of these factors as mentioned above on the operation performance of motor. In this paper, a general finite element method (FEM) based d-q axis variable modeling method of PMSM was proposed. A general nonlinear d-q axis variable mathematic model of PMSM was established taking account of the effects of saturation and space harmonics, in which the d-q axis inductance and the flux linkage excited by PM were obtained from the finite element solutions by using Ansoft. A new M function based simulation model was implemented in Simulink using the equation of the established nonlinear model. The simulation and experimental results of a PMSM show that the proposed nonlinear model is correct and has perfect precision, which provides a fast, accurate and efficient modeling method for the characteristic and the drive system dynamic precise analysis of PMSM.
This paper describes the drivers, characteristics and major technical components of smart grid. The associated smart grid benefits, challenges and worldwide implementations are also summarized. It is emphasized that although the smart grid implementation is promising, it faces huge challenges. The migration to smart grid is a long journey when various technologies will coexist which requires thoughtful planning. Demand response and distributed renewable resource integration can serve the needs of sustainability and relieve the demand for transmission and generation capacities. While many interests and efforts have been taking on advanced transmission operations (ATO), other smart grid components as advanced metering infrastructure (AMI), advanced distribution operations (ADO) and advanced asset management (AAM) should be investigated as well. Reconfigurable distribution network and integrated energy and communication system architecture (IECSA) are the foundation of future smart grid, so they should be integrated in system planning from now. Smart grid implementation will boost the developments of various technologies and wide range of industrial participants should be encouraged.
Field-weakening technology is important for permanent magnet synchronous machine (PMSM) control in wide speed range applications. In deep field-weakening operation, saturation of current regulators may lead to losing control and even damages. This paper analyzed the reason why current saturation happens for conventional field-weakening algorithm. It is concluded that precise limitation of d-axis current is necessary to keep the system under control. New control algorithm is proposed to prevent losing control from happening. It is verified by experimental result that the speed range of PMSM is enhanced by the proposed field-weakening algorithm.
Investigation on noise discrimination network (NDN) techniques for conducted electromagnetic interference (EMI) noise on power line is performed including optimization of network topology, performance improvement of circuit elements and the parameter extraction of NDN by using S-parameter measurement. Results show that insertion loss of NDN can be improved about 3dB and noise rejection ratio about 15dB with these techniques. Additionally, two experiments about noise diagnosis and suppression for both conductive EMI noise of SMPS and radiated noise of power line communication (PLC) system have been completed by applying the new NDN to show the efficiency of techniques.
In many applications such as electrical vehicle and computer numerical control machine, induction motor (IM) needs large speed range operation with constant output power. A new current and voltage trajectories control scheme for the field weakening operation of induction motor drive was presented. The proposed scheme allows the motor to exploit the maximum torque capability in the whole speed range with the constraints of maximum voltage and current of the motor and inverter. In the proposed control algorithm the lookup table is not required for currents references obtaining, which reduces the dependence on the motor parameters. The smooth transition between maximum torque per ampere (MTPA) and field weakening regions is implemented according to the integration of the time of zero voltage vector in SVPWM method. The validity of the proposed field weakening technique is validated by computer simulations and experimental tests with a 5.5 kW induction motor drive system.
In order to meet the operation requirement under time-variable inertia and time-variable load condition, an adaptive torque control method with anti-disturbance is proposed for permanent magnet synchronous motor (PMSM) servo system. With time-variable inertia, a Landau discrete-time recursive algorithm used to estimate the inertia is adopted. According to the rules, the parameters of speed controller were regulated by the estimated inertia, which guarantees good dynamic and static performance in servo system. Under time-variable load condition, a simple reduced-order observer is established to identify the load torque. And with the estimated value, speed disturbances caused by heavy load can be adaptively compensated which improves system robustness. Experimental results show that the proposed adaptive algorithm is effective and the convergence rate of inertia identification is fast. Compensation measure used in this scheme has strong robustness to the change of system parameters and the disturbance, and it can be applied to some drive fields that have time-variable load and inertia changing slowly.