Calculation and analysis of losses of magnetic-valve controllable reactor

Magnetic-valve controllable reactor(MCR)has characteristics of DC bias and different types of magnetic flux density in the magnetic circuit and winding current distortion.These characteristics not only lead to loss calculation method of MCR different from that of power transformer,but also make it more difficult to calculate the core loss and wingding loss of MCR accurately.Our study combines core partition method with dynamic inverse J-A model to calculate the core loss of MCR.The winding loss coefficient of MCR is proposed,which takes into account the influence of harmonics and magnetic flux leakage on the winding loss of MCR.The result shows that the proposed core loss calculation method and winding loss coefficient are effective and correct for the loss calculation of MCR.

MPC of distillation column with side reactors for methyl acetate

This paper focuses on the dynamic control of distillation column with side reactors(SRC) for methyl acetate production. To obtain the optimum integrated structure and steady state simulation, the systematic design approach based on the concept of independent reaction amount is applied to the process of SRC for methyl acetate production. In addition to the basic control loops, multi-variable model predictive control modular with methyl acetate concentration and temperature of sensitive plate is designed. Then, based on process simulation software Aspen Plus, dynamic simulation of SRC for methyl acetate production is used to verify the effectiveness of the control scheme.

Adaptive output-feedback power-level control for modular high temperature gas-cooled reactors

Small modular reactors(SMRs) are beneficial in providing electricity power safely and viable for specific applications such as seawater desalination and heat production. Due to its inherent safety feature, the modular high temperature gas-cooled reactor(MHTGR) is considered as one of the best candidates for SMR-based nuclear power plants. Since its dynamics presents high nonlinearity and parameter uncertainty, it is necessary to develop adaptive power-level control, which is beneficial to safe, stable, and efficient operation of MHTGR and is easy to be implemented. In this paper, based on the physically-based control design approach, an adaptive outputfeedback power-level control is proposed for MHTGRs. This control can guarantee globally bounded closedloop stability and has a simple form. Numerical simulation results show the correctness of the theoretical analysis and satisfactory regulation performance of this control.

MHD Stability Analysis and Flow Controls of Liquid Metal Free Surface Film Flows as Fusion Reactor PFCs

Numerical and experimental investigation results on the magnetohydrodynamics（MHD） film flows along flat and curved bottom surfaces are summarized in this study. A simplified modeling has been developed to study the liquid metal MHD film state, which has been validated by the existing experimental results. Numerical results on how the inlet velocity（V）, the chute width（W） and the inlet film thickness（d0） affect the MHD film flow state are obtained. MHD stability analysis results are also provided in this study. The results show that strong magnetic fields make the stable V decrease several times compared to the case with no magnetic field,especially small radial magnetic fields（Bn） will have a significant impact on the MHD film flow state. Based on the above numerical and MHD stability analysis results flow control methods are proposed for flat and curved MHD film flows. For curved film flow we firstly proposed a new multi-layers MHD film flow system with a solid metal mesh to get the stable MHD film flows along the curved bottom surface. Experiments on flat and curved MHD film flows are also carried out and some firstly observed results are achieved.

Mathematical model analysis of new-type magnetic integrated CRT considering magnetic leakage

A novel magnetic integrated controllable reactor of transformer type(CRT)has the advantages of simple structure,flexible assembly,convenient maintenance and practicability.To analyze its operation characteristics accurately,we establish corresponding equivalent mathematical model considering magnetic leakage based on magnetic circuit and circuit dualistic transformation method.The distribution of magnetic leakage field of each winding is analyzed qualitatively,and the analytical calculation formulas of magnetizing inductance and leakage inductance of each winding are derived.Based on this,the analytical calculation formulas of short-circuit impedance and winding current of CRT under different working conditions are derived.The field-circuit coupling finite element model of the magnetic integrated CRT is established to simulate the current of each winding under different working conditions.The results show that the analytical calculation results of each winding current have good consistency with the finite element calculation results,indicating the validity of CRT equivalent mathematical model and correctness of the analytical formulas of leakage inductance,short-circuit impedance and winding current of CRT.The working winding current of CRT is increasing gradually with the operation of control winding in turn to realise the transition of CRT compensation capacity from zero to a rated value.

Stability Improvement of Power System by Using PI ＆ PD Controller

This paper presents the model of a SVC （Static VAR Compensator） which is controlled externally by a PI （Proportional Integral） ＆ PD （Proportional Differential） controllers for the improvements of voltage stability and damping effect of an on line power system. Both controller parameters has been optimized by using Ziegler-Nichols close loop tuning method. Both single phase and three phase （L-L） faults have been considered in the research. In this paper, a power system network is considered which is simulated in the phasor simulation method ＆ the network is simulated in four steps; without SVC, With SVC but no externally controlled, SVC with PI controller ＆ SVC with PD controller. Simulation result shows that without SVC, the system parameters become unstable during faults. When SVC is imposed in the network, then system parameters become stable. Again, when SVC is controlled externally by PI ＆ PD controllers, then system parameters becomes stable in faster way then without controller. It has been observed that the SVC ratings are only 50 MVA with controllers and 200 MVA without controllers. So, SVC with PI ＆ PD controllers are more effective to enhance the voltage stability and increases power transmission capacity of a power system. The power system oscillations are also reduced with controllers in compared to that of without controllers. So with both controllers the system performance is greatly enhanced.

A Novel Soft Start Method of Super Large Capacity High Voltage Motor

The large current generated by starting directly of super large capacity and high voltage induction motor would have a huge impact on the grid as well as the motor itself.The variation of the power factor and electromagnetic torque during direct start of motors with different capacity and voltage levels are obtained.Aiming at the problem that the secondary impact of auto-transformer starter is too large and the cost of magnetic control starter is too high,the auto-transformer and magnetic control soft start method of super large capacity and high voltage motor is proposed and the basic working principle is analyzed.The calculation formula of cost for magnetic control soft starter and auto-transformer and magnetic control soft starter is deduced,and specific examples are analyzed and compared.It is concluded that the choice of auto-transformer with appropriate tapping ratio can greatly reduce the cost of auto-transformer and magnetic control soft starter compared with the other one.Finally,the simulation and experiment results show that the start method can effectively avoid secondary current impact and constrain the motor starting current to less than 2.5 times the rated current.

Static Var Compensator to Increase the Availability of a Colombian Oil Field

The paper describes the application of a static var compensator to improve the electrical system of the ACN （Cravo Norte Association） oil field in Colombia. The paper summarizes the application, including system aspects that require special control functions in the SVC （static var compensator） regulator. Several important benefits for the system operation are demonstrated, such as increased power transmission import over an existing 230 kV network, dynamic bus voltage stabilization for various load conditions, including system outages and load rejection, and reduction of variable speed drive shutdowns by up to 95%. Some relevant design features of the SVC are treated, as well.

Fault component integrated impedance-based pilot protection scheme for EHV/UHV transmission line with thyristor controlled series capacitor(TCSC) and controllable shunt reactor(CSR)

This paper analyzes the fundamental frequency impedance presents a novel transmission line pilot protection scheme characteristic of a thyristor controlled series capacitor （TCSC） and based on fault component integrated impedance （FCII） calculated for a transmission line with TCSC and controllable shunt reactor （CSR）. The FCII is defined as the ratio of the sum of the fault component voltage phasors of a transmission line with TCSC and CSR to the sum of the fault component current phasors where all the phasors are determined at both line＇s terminals. It can be used to distinguish internal faults occurring on the line from external ones. If the fault is an external one the FCII reflects the line＇s capacitive impedance and has large value. If the fault is an internal one on the line the FCII reflects the impedance of the equivalent system and the line and is relatively small. The new pilot protection scheme can be easily set and has the fault phase selection ability and also it is not affected by the capacitive current and the fault transition resistance. It is not sensitive to compensation level and dynamics of TCSC and CSR. The effectiveness of the new scheme is validated against data obtained in ATP simulations and Northwest China 750 kV Project.

The nitritation performance of biofilm reactor for treating domestic wastewater under high dissolved oxygen

The objective of this study was to investigate the nitritation performance in a biofilm reactor for treating domestic wastewater.The reactor was operated in continuous feed mode from phases 1 to 3.The dissolved oxygen（DO）was controlled at 3.5–7 mg/L throughout the experiment.The biofilm reactor showed excellent nitritation performance after the inoculation of nitrifying sludge,with the hydraulic retention time being reduced from 24 to 7 hr.Above 90%nitrite accumulation ratio（NAR）was maintained in phase 1.Afterwards,nitratation occurred with the low NH4^＋–N concentration in the reactor.The improvement of NH4^＋–N concentration to 20–35 mg/L had a limited effect on the recovery of nitritation.However,nitritation recovered rapidly when sequencing batch feed mode was adopted in phase 4,with the effluent NH4^＋-N concentration above 7 mg/L.The improvement of ammonia oxidizing bacteria（AOB）activity and the combined inhibition effect of free ammonia（FA）and free nitrous acid（FNA）on the nitrite oxidizing bacteria（NOB）were two key factors for the rapid recovery of nitritation.Sludge activity was obtained in batch tests.The results of batch tests had a good relationship with the long term operation performance of the biofilm reactor.

A logic-based controller for the mitigation of ventilation air methane in a catalytic flow reversal reactor

The control system of a catalytic flow reversal reactor （CFRR） for the mitigation of ventilation air methane was investigated. A one-dimensional heteroge- neous model with a logic-based controller was applied to simulate the CFRR. The simulation results indicated that the controller developed in this work performs well under normal conditions. Air dilution and auxiliary methane injection are effective to avoid the catalyst overheating and reaction extinction caused by prolonged rich and lean feed conditions, respectively. In contrast, the reactor is prone to lose control by adjusting the switching time solely. Air dilution exhibits the effects of two contradictory aspects on the operation of CFRR, i.e., cooling the bed and accumulating heat, though the former is in general more prominent. Lowering the reference temperature for flow reversal can decrease the bed temperature and benefit stable operation under rich methane feed condition.