J.-J. Simond

High-Order Modeling of Hydraulic Power Plant in Islanded Power Network

Numerical simulations of the transient operation of an islanded power network subject to load rejections are performed. The islanded power network case study consists of a 1-GW hydroelectric power plant featuring four generating units, a long penstock, and a surge tank connected to four 1.3-GW thermal power plants and passive consumers. The modeling of every network component is described and special care is paid to the modeling of the hydroelectric power plant. In particular, the high-order modeling used for these investigations enables the detailed simulation of water hammer, mass oscillations, and nonlinear hydraulic characteristics of the turbines interacting with the electrical components of the network. Moreover, the stability analysis of the systems is performed for different load conditions and the damping performances of a power system stabilizer IEEE PSS2B are investigated.

Investigation of Control Strategies for Variable-Speed Pump-Turbine Units by Using a Simplified Model of the Converters

This paper presents the modeling, simulation, and analysis of the dynamic behavior of a fictitious 2 × 320 MW variable-speed pump-turbine power plant, including a hydraulic system, electrical equipment, rotating inertias, and control systems. The modeling of the hydraulic and electrical components of the power plant is presented. The dynamic performances of a control strategy in generating mode and one in pumping mode are investigated by the simulation of the complete models in the case of change of active power set points. Then, a pseudocontinuous model of the converters feeding the rotor circuits is described. Due to this simplification, the simulation time can be reduced drastically (approximately factor 60). A first validation of the simplified model of the converters is obtained by comparison of the simulated results coming from the simplified and complete models for different modes of operation of the power plant. Experimental results performed on a 2.2-kW low-power test bench are also compared with the simulated results coming from both complete and simplified models related to this case and confirm the validity of the proposed simplified approach for the converters.

Modeling, Simulation, and Test of a Three-Level Voltage-Source Inverter With Output

This paper presents the modeling, the detailed simulation and the test of an efficient medium voltage adjustable speed drive. The system consists of a three-level neutral-point clamped (NPC) inverter supplied by a 12-pulse rectifier. To achieve a motor-friendly supply, an LC filter is inserted between inverter output terminals and induction motor terminals. A direct torque control (DTC) tunes the inverter. The full power circuits and the digital control scheme have been implemented and simulated. Simulation results have been compared successfully with measurements, in steady state and transients.

LC

This paper presents a combined analytical and finite-element (FE) method for computation of the no-load voltage waveform of laminated salient-pole synchronous generators. The described method takes into account saturation effects as well as the damper bar currents due to the slot pulsation field. The method calculates first the damper bar currents and then includes them in the calculation of the no-load voltage. The combination of magnetostatic two-dimensional (2-D) FE simulations for calculating the magnetic coupling between the machine windings and of an analytical resolution results in a very precise prediction of the no-load voltage. At the same time, simulation time is drastically reduced compared with transient magnetic 2-D FE simulations. The method was verified on several examples, comparing the obtained results (damper bar currents and no-load voltage) with results obtained from transient magnetic FE simulations and, in one case, with the measured no-load voltage.

Filter and Direct Torque Control

The current source thyristor inverter is still today a suitable choice for supplying high power adjustable speed drives for pumps or compressors. This paper presents a 12-pulse LCI (load commutated inverter) synchronous drive for a 20 MW compressor, it focuses on the following main aspects: modeling of the complete drive system, numerical simulation and comparison between calculated and measured values of the pulsating torque components in steady-state operations. The modeling of the six-phase synchronous motor is obtained by using a new virtual test-platform for large electrical machines. The pulsating torque components are measured in real time with a digital transient torque measurement device.

Computation of the no-load voltage waveform of laminated salient-pole synchronous generators

The present paper investigates the complete regulation strategy for a large double-fed asynchronous motor-generator equipped with a 3-level VSI cascade for applications mainly in the field of pumped storage plant. For the present application, the specific problem of the DC link capacitors voltage balancing is investigated. Also a sensorless method for the determination of the rotor angle is proposed and verified in practice. Measurements of the system performed on a laboratory low power system are discussed and compared to simulations.

12-pulse LCI synchronous drive for a 20 MW compressor modeling, simulation and measurements

The dynamic performances of variable speed and fixed speed units are compared in the case of 2 × 320 MW pumped storage power plant. The case study of the pumped storage power plant with standard synchronous machine with PSS is presented and, then, the corresponding variable speed system is designed for this case. Unsteady numerical simulations of both architectures enable to demonstrate that the variable speed architecture improves the power system stability characteristics for both the local and the inter-area modes of oscillation. Moreover, the damping of active power oscillations originated by the part load operation of the pump-turbine in generating mode is investigated as well.

Double-fed asynchronous motor-generator equipped with a 3-level VSI cascade

This paper presents the modeling, the detailed simulation and the test of an efficient medium voltage adjustable speed drive. The system consists of a three-level neutral-point clamped (NPC) inverter supplied by a 12-pulse rectifier. To achieve a motor-friendly supply, an LC filter is inserted between inverter output terminals and induction motor terminals. A direct torque control (DTC) tunes the inverter. The full power circuits and the digital control scheme have been implemented and simulated. Simulation results have been compared successfully with measurements, in steady state and transients.

Dynamical Behavior Comparison Between Variable Speed and Synchronous Machines With PSS

This paper presents a numerical simulation study of the transient behavior of a 2x340MW pump-turbine power plant, where the results show an unstable behavior at runaway. First, the modeling of hydraulic components based on equivalent schemes is presented. Then, the 2 pump-turbine test case is presented. The transient behavior of the power plant is simulated for a case of emergency shutdown with servomotor failure on Unit 1. Unstable operation at runaway with a period of 15 seconds is properly simulated using a 1-dimensional approach. The simulation results points out a switch after 200 seconds of the unstable behavior between a period of oscillations initially of 15 seconds to a period of oscillation of 2.16 seconds corresponding to the hydraulic circuit first natural period. The pressure fluctuations related to both the rigid and elastic water column mode are presented for oscillation mode characterization. This phenomenon is described as a switch between a rigid and an elastic water column oscillation mode. The influence of the rotating inertia on the switch phenomenon is investigated through a parametric study.

Modeling, simulation and test of a three-level voltage source inverter with output LC filter and direct torque control

This paper presents a combined analytical and FEM method for prediction of the no-load voltage waveform of laminated salient-pole synchronous generators. The described method takes into account saturation effects as well as the damper bar currents due to the slot pulsation field. The method calculates first the damper bar currents and then includes them in the calculation of the no-load voltage. The combination of magnetostatic 2D finite element simulations for calculating the magnetic coupling between the machine windings and of an analytical resolution, results in a very precise prediction of the no-load voltage. At the same time simulation time is drastically reduced, compared to transient magnetic 2D finite element simulations. The method was verified on several examples, comparing the obtained results (damper bar currents and no-load voltage) to results obtained from transient magnetic finite element simulations and in one case to the measured no-load voltage. A tool, implementing this method, is currently used by one of our major industrial partners. It is planned to use this method for analysis of the effects of various rotor eccentricity conditions in salient-pole synchronous generators.