Voltage Angle Control Research Articles

Voltage Angle Control for a BLDC Motor and Controller Gain Design

Voltage Angle Control for a BLDC Motor and Controller Gain Design

Complying the LVRT grid code requirement of a fixed speed wind energy system using unified voltage and pitch angle control strategy

This paper proposes a Unified Voltage and Pitch angle Control (UVPC) strategy for fixed speed wind farm. The focus put on guaranteeing the LVRT grid code requirement when the wind farm subjected to severe faults. The UVPC consist of static synchronous compensator (STATCOM) voltage control loops with adequate pitch angle control loops which are coordinated to enhance the low-voltage ride-through capability of the wind generators thereby, complying the low voltage ride through (LVRT) grid code requirement as desired by the Germany grid code. Different scenarios such as system without STATCOM and pitch-angle controller, with STATCOM only, and system with STATCOM and pitch-angle control (i.e. UVPC) are simulated. The simulation results show that the adoption of STATCOM and pitch angle controller fulfilling the LVRT grid code requirement to ensure the continuous operation of wind turbines. Furthermore, a concept of critical clearing time (CCT) is discussed and its utility has been emphasized. Calculations, simulations and measurements provide how the increased STATCOM rating can offer an enhanced stability margin.

Six-Step Operation of a Symmetric Dual Three-Phase PMSM With Minimal Circulating Currents for Extended Speed Range in Electric Vehicles

Automotive applications demand high efficiency, good reliability, and a wide operating speed range within limited dc bus voltage constraints. In this article, a zero degree displacement dual three-phase permanent magnet synchronous machines (PMSM) is derived from an original three-phase PMSM to enhance the power rating as well as the operating speed range. The proposed topology can be used as an alternative to the conventional configuration of three-phase PMSM with a bidirectional dc–dc converter for electric vehicles. Even though the commonly used dual three-phase PMSM with split-phase winding eliminates the sixth harmonic torque pulsation, a large circulating current is generated during six-step operation, which results in additional stator copper loss. In this article, six-step operation of the symmetric dual three-phase PMSM with zero degree winding displacement is proposed to achieve maximum inverter utilization. Both harmonic circulating current and torque pulsation were observed to be within satisfactory levels using this configuration. A changeover algorithm is also proposed to enable a smooth transition between closed-loop current vector control during low and medium speed operation to open-loop six-step voltage angle control for high speed operation. The performance of the proposed method is experimentally validated on a 3-kW dual three-phase PMSM drive.

Development of FW and MTPV Control for SynRM via Feedforward Voltage Angle Control

In order to develop a wide speed range operation of the synchronous reluctance motor (SynRM) drive system for constant torque, constant power, and reduced power regions, an extended speed control (ESC) with maximum efficiency (ME), flux weakening (FW), and maximum torque per voltage (MTPV) is proposed in this article. First, a conventional FW control system with field-oriented control is introduced. Moreover, to achieve the ME operation, a lookup table of the results of ME analysis by using the finite element analysis technology is adopted to produce the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current commands for the current control mode of the SynRM in the constant torque region. Furthermore, the FW voltage controller is employed to produce the incremental value of the stator voltage command to achieve the maximum voltage limit. In addition, a novel feedforward-based voltage angle controller with an MTPV limiter is designed to generate the voltage angle command for the voltage control mode in the constant power and reduced power regions. Finally, the proposed ESC system is implemented in a 32-b floating-point digital signal processor TMS320F28075 and its robustness and effectiveness are verified by some experimental results.

Performance investigation on ANFIS and FFNN assisted direct and indirect PV-fed switched reluctance motor water pumping system

ABSTRACT Alternative energy sources have impacted as the ideal choice for reducing the burden on the grid and producing clean energy for water pumping. As an alternative to conventional motors for pumping, switched reluctance motor (SRM) is promising, cost-effective and highly efficient. This paper presents artificial intelligence (AI) supported variable voltage angle control (VVAC) for indirect and direct photovoltaic (PV)-fed SRM-based water pumping systems (WPS). Proposed feedforward neural network (FFNN) and adaptive neuro-fuzzy inference system (ANFIS) models are simulated and analysed for their percentage average error and real-time execution speed in the dSPACE-1104 control board. ANFIS resulted in 1/10th reduction of execution time and improved performance accuracy in contrast to FFNN counterparts. A 4kW, 8/6 SRM model, has been developed in MATLAB/Simulink environment to validate the proposed system for both direct and indirect schemes. Further, the performance comparison of peak current, RMS current, torque ripple, and efficiency for direct and indirect PV-fed systems are presented in this work. These comparative assertions reveal the feasibility of both the methods with good performance. Moreover, a reduction in overall system size and cost with the absence of an intermediate converter, the direct method provides a reduced torque ripple as compared to the indirect counterpart.

Distributed Mixed Voltage Angle and Frequency Droop Control of Microgrid Interconnections With Loss of Distribution-PMU Measurements

Recent advances in distribution-level phasor measurement unit (D-PMU) technology have enabled the use of voltage phase angle measurements for direct load sharing control in distribution-level microgrid interconnections with high penetration of renewable distributed energy resources (DERs). In particular, D-PMU enabled voltage angle droop control has the potential to enhance stability and transient performance in such microgrid interconnections. However, these angle droop control designs are vulnerable to D-PMU angle measurement losses that frequently occur due to the unavailability of a global positioning system (GPS) signal for synchronization. In the event of such measurement losses, angle droop controlled microgrid interconnections may suffer from poor performance and potentially lose stability. In this paper, we propose a novel distributed mixed voltage angle and frequency droop control (D-MAFD) framework to improve the reliability of angle droop controlled microgrid interconnections. In this framework, when the D-PMU phase angle measurement is lost at a microgrid, conventional frequency droop control is temporarily used for primary control in place of angle droop control to guarantee stability. We model the microgrid interconnection with this primary control architecture as a nonlinear switched system and design distributed secondary controllers to guarantee stability of the network. Further, we incorporate performance specifications such as robustness to generation-load mismatch and network topology changes in the distributed control design. We demonstrate the performance of this control framework by simulation on a test 123-feeder distribution network.

Active Power Regulation of a Storage Power Plant (SPP) with Voltage Angle Control as Ancillary Service

Electrical Energy Storage (EES) plays an increasingly important role to balance the intermittent power generation and demand, thus ensuring a more reliable network. An example of such an EES is the Storage Power Plant (SPP). It has been proved in previous studies that the SPP not only improves the power supply security but also reduces redispatch costs. However, its protection features against overcurrent and exceeding of its generation limit or storage capacity have not been discussed yet. In reality, such events can occur, leading to unexpected grid failures as a worst case scenario. Thus, the aim of this paper is to exhibit the behavior of a controller model which has been implemented in the SPP to protect the power plant during such situations. In this investigation, once the SPP’s active power output is about to surpass its limit, the power plant automatically switches to a different mode of operation at the threshold value to prevent this from happening. In this manner, the SPP can protect itself autonomously and also helps to create a more robust system.

Flux-Weakening in PMSM Drives: Analysis of Voltage Angle Control and the Single Current Controller Design

Voltage angle control not only can solve the problem that two current regulators of traditional algorithms conflict with each other but also has the advantage of maximum utilization of the dc-link voltage. Based on the basic equations of permanent-magnet synchronous motors (PMSM) in $i_{d}$ – $i_{q}$ coordinate plane, the principle of voltage angle control is analyzed and a single $q$ -axis current regulator-variable voltage angle control method is proposed as the novel approach for the flux-weakening operation of PMSM over a wide range of speed in motoring and generating mode. The proposed method enables the fast dynamic response of current when current reference changes and eliminates the transition between the motoring and generating operation. The results of simulation and experiment demonstrate the effectiveness of the proposed control method.

Intermediate Voltage Variation-Based Interconnecting Transformer Design for Voltage and Phase Angle Control With Coupled Field FEA Studies

A 160-MVA, 220/132/33-kV autotransformer is commonly used as an intermediate connecting transformer (ICT) in an electrical power transmission network. The modified design of such an ICT in order to get a phase angle control along with the voltage control, by intermediate voltage variation, is reported in this paper. Estimation of stray loss and core loss is done both by analytically and realizing 2-D and 3-D models by a finite-element analysis (FEA) method. A 3-D FEA design is further extended with arrangement of shunts to limit the stray loss and the thermal impact. Multiphysics simulation platform is used to link magnetostatic, steady-state thermal and structural FEA models. The composite FEA simulation approach used in this study enables steady-state thermal analysis of a transformer by importing stray loss from the magnetostatic model and the structural deformation in the transformer due to hot-spot temperature. To validate the proposed design, a 1-kVA, 415/230-V, three-phase transformer is designed, built, and tested in the laboratory. Voltage and phase angle at various operating conditions calculated analytically, obtained through FEA and measured experimentally, are in close agreement.

Power Re-Dispatch Reduction with Nodal Voltage Angle Control in Electrical Energy Supply Systems

Abstract In the future, the electrical power supply networks will be transformed from conventional power plant structures with inertia to a complete inertia independent system. Such systems will include storages for different generation speed together with power electronic converters. In this paper, a novel method is proposed to control the electrical power distribution by these new power plants. All the control principles necessary involving spinning reserve, primary control and secondary control depending on frequency are substituted by a comprehensive angle control of the nodal voltages in the transmission and distribution network. It is observed that whenever the power requirement of the loads increase, the slack generators satisfy this rising demand with the power stations closest to the point of increasing consumption automatically producing the most power. This drastically reduces the heavy load flow and the need for general power re-dispatch measures. Reducing power re-dispatch would not only save millions of Euros on an annual basis but also lead to the formation of a more secure electrical network.

Unaprijeđeno upravljanje momentom visokobrzinskog pogona s asinkronim motorom bez mjerenja brzine

This paper presents improved torque control scheme for a high speed sensorless induction motor drive. The proposed high speed torque control scheme substitutes the flux oriented control by the voltage angle control in the flux weakening regime. This scheme uses maximum of available inverter voltage, alleviates well known problems of current control schemes in conditions with insufficient voltage margin and avoids the influence of estimated speed error to the achieved flux level. The algorithm uses similar slip control as flux oriented control algorithm, but is applied without an outer flux trajectory reference which is typical for the flux weakening, providing a fast and well damped torque response even if error in estimated speed is present. Experiments confirm the effectiveness of proposed torque control algorithm, smooth transition from the flux oriented control in the base speed region to the voltage angle control in the flux weakening, superior dynamic performance of the voltage angle torque control, and its robustness to an estimated rotor speed error.

Improved Torque Control of High Speed Shaft-Sensorless Induction Motor Drive

This paper presents improved torque control scheme for a high speed sensorless induction motor drive. The proposed high speed torque control scheme substitutes the flux oriented control by the voltage angle control in the flux weakening regime. This scheme uses maximum of available inverter voltage, alleviates well known problems of current control schemes in conditions with insufficient voltage margin and avoids the influence of estimated speed error to the achieved flux level. The algorithm uses similar slip control as flux oriented control algorithm, but is applied without an outer flux trajectory reference which is typical for the flux weakening, providing a fast and well damped torque response even if error in estimated speed is present.Experiments confirm the effectiveness of proposed torque control algorithm, smooth transition from the flux oriented control in the base speed region to the voltage angle control in the flux weakening, superior dynamic performance of the voltage angle torque control, and its robustness to an estimated rotor speed error.

Six-Step Operation of PMSM With Instantaneous Current Control

Six-step operation has many advantages in permanent-magnet synchronous machine (PMSM) drives such as maximum power utilization and widened flux-weakening region. However, due to the maximum utilization of inverter output, saturation of current regulator makes it difficult to maintain instantaneous current control capability. Accordingly, in most of conventional research studies, the six-step operation has been implemented by voltage angle control without current regulation, whose dynamic performance is quite unsatisfactory. This paper proposes a control scheme for the six-step operation of PMSM with enhanced dynamic performance of current control. By collaborative operation of dynamic overmodulation, flux weakening, and a technique for enhanced dynamic performance, the six-step operation is realized without losing instantaneous current control capability. Simulations and experiments are carried out to verify the effectiveness of the proposed control scheme. The experimental results show 17% extension of the constant torque region and 27% enhancement of torque capability at three times of the base speed.

Control methods of the switched reluctance motor in electric vehicle during acceleration

In this paper, the equations describing the performance of the electric vehicle are derived. Performance characteristics for each part in the vehicle system are obtained when the vehicle is accelerated under voltage, turn on, and turn off angle control. A comparison between the different methods of control is established. From these comparisons, it can be noticed that the acceleration time, for the case at which the turn on angle is controlled, will be smaller than that for the other cases; also the motor efficiency, at the voltage control method, has the highest value especially at the higher values of the vehicle speed.

Voltage angle direct torque control of induction machine in field-weakening regime

This study presents a novel algorithm for the induction motor torque control in field-weakening region. The proposed method insures maximum DC bus utilisation and extends the torque–speed curve up to the system limits. Controller is based on the stator voltage angle control. It provides full DC-link disturbance rejection and offers the torque response time sufficient for most applications. The algorithm is simple, without neither the outer flux loop nor the inner current loop. Dynamic response is preserved over wide speed range by means of gain-scheduling. Simulations and experiments prove an ease of implementation and the robustness of the proposed solution. This study comprises analytical considerations, simulation results, a detailed description of implementation steps and extensive experimental results.

Implementation of unified power flow controller and verification for transmission capability improvement

This paper describes a unified power flow controller (UPFC) miniature model developed for performing system feasibility studies. The system and control configuration of the model are first described, then protection and control for transmission capability improvement are verified using a real time analog simulator. The series portion of the UPFC has three control modes (perpendicular voltage control, impedance control and voltage angle control) which are used for power flow control and/or power system stabilizing control. Various tests were performed to compare control modes. The perpendicular voltage control is proposed as the simplest and most practical mode because the capacity of the shunt compensator is minimized, and power flow control sensitivity is maintained over a wide range of angle.

Voltage, frequency, and phase-difference angle control of PWM inverters-fed two-phase induction motors

A phase-difference angle (PDA) controlled pulsewidth-modulated (PWM) inverter is proposed for a two-phase induction motor adjustable speed drive. Output waveforms are fixed over the whole operating range of the motor. The motor torque is controlled not by the modulation of the phase voltage, but by the PDA. Based on the selected harmonic elimination (SHE) PWM technique, the commutation angles of the output voltage are calculated. Several characteristics of the two-phase induction motor driven by the PDA inverter are analyzed. A hybrid PWM inverter is also proposed to compensate for the degradation of the efficiency at small PDA. Not only the PDA but also the voltage amplitude and frequency are used as the parameters for controlling the torque of the motor in the hybrid inverter. The speed characteristics of the two-phase induction motor driven by the hybrid PWM inverter are more flexible than when the motor is driven by the conventional PWM inverter, which requires adjustable communication angles. >