Dq Coordinate System Research Articles

Sliding mode observer-based fault diagnosis and continuous control set fault tolerant control for PMSM with demagnetization fault

A fault detection, estimation and fault tolerant control scheme for demagnetization fault in the permanent magnet synchronous motor systems is proposed in this paper. When demagnetization fault occurs, the system will deviate from the normal state severely. To facilitate the calculation, the demagnetization fault is converted to the dq coordinate system for processing and the resistance change is modeled as the system uncertainty, and the effect of the uncertainty on the system is analyzed. Then a fault detection observer is designed to detect the fault occurrence time, and a sliding mode observer based fault estimation algorithm is designed to estimate the fault and disturbance information. The observer parameters are determined by linear matrix inequality. When the fault information is obtained, a continuous control set fault tolerant control scheme is presented to minimize the impact of fault as far as possible. Finally, experimental results provide evidence of the feasibility of the suggested algorithm.

Model Predictive Control of Counter-Rotating Motors for Underwater Vehicles Considering Unbalanced Load Variation

The propulsion system for underwater vehicles, driven by a counter-rotating permanent magnet synchronous motor (CRPMSM), can enhance the operational stability and efficiency of the vehicle. Due to the influence of complex underwater flows, the load imbalance of CRPMSM’s dual counter-rotating rotors may lead to severe issues of dual-rotor desynchronization rotation. Combining traditional vector control (VC) with master-slave control strategies can address the desynchronization problem when CRPMSM’s load changes. However, it results in significant speed fluctuations and a long transition time during the transition from load disturbance to synchronous rotation. This paper introduces a model predictive control (MPC) strategy to effectively resolve this issue. The incremental MPC model is established based on the mathematical model of CRPMSM in the dq coordinate system. The predictive control system forecasts the d- and q-axis components of stator currents for the next four control cycles. It selects the optimal control increments to minimize the cost function based on current predictions and different inverter voltage states. The obtained optimal d- and q-axis components of stator voltage are used to control CRPMSM under unbalanced load disturbances. Simulation results demonstrate that, compared to the VC strategy, CRPMSM utilizing the MPC strategy exhibits better dynamic performance with faster speed response and reduced torque fluctuations during load and speed variations.

Predictive direct control strategy of unified power quality conditioner based on power angle control

The unified power quality conditioner (UPQC), based on power angle control (PAC), addresses the power distribution issue and enhances equipment utilization between two active power filters (APF) of UPQC by employing conventional linear control algorithms that have complex control structures and exhibit challenges in adjusting controller parameters and control delays. This study proposes a UPQC predictive direct control strategy based on power angle control (PDCS-PAC). We combine the direct control strategy with the finite control set model predictive control (FCS-MPC) to establish the UPQC finite set model predictive direct control system model in the dq coordinate system. This approach simplifies the controller structure and alleviates the control algorithm’s complexity. Based on a detailed analysis of the PAC mechanism, an instantaneous power angle determination method is proposed based on the reactive power equalization technique, and a predictive direct control strategy given the current generation mechanism is constructed for the series and shunt sides of the UPQC, considering the active power balance of the UPQC system and the principle of constant load fundamental voltage amplitude. Finally, we construct a simulation platform and a laboratory prototype to validate the feasibility and efficacy of the proposed control strategy.

Моделирование динамических режимов работы электроприводов с системой векторного управления синхронным двигателем

Purpose: The purpose of the work is a comparative assessment of dynamic processes in electric drives with a vector control system for permanent magnets synchronous motors and various methods of stator voltage modulation. To achieve this purpose, a mathematical description of a synchronous motor in a rotating dq coordinate system is given, and a mathematical model of a vector control system is developed. The model of the vector control system takes into account the decoupling of stator current control loops and proposes two options for generating a current reference along the d-axis, ensuring the efficiency of energy conversion processes at rotation speeds below the nominal value, depending on the design of the motor rotor. Algorithms for scalar pulse-width and space-vector modulation of motor stator voltage for a frequency converter with a two-level autonomous voltage inverter are presented. Methods: When developing mathematical models and algorithms, methods from the theory of electric drive and the theory of automatic control have been used. The developed mathematical models and algorithms are implemented in the Matlab Simulink software package. Results: The results of modeling dynamic processes in electric drives (mechanical characteristics, stator currents, stator current total harmonic distortion) are presented, which have shown the performance of the developed models and algorithms. Practical significance: The choice of modulation type does not affect the mechanical characteristics of the electric drive, but does affect the harmonic composition of the stator current. The greatest effect from the use of space-vector modulation algorithms is manifested at reduced values of the frequency of the stator current and partial load torque on the rotor shaft.

VSC control strategy for HVDC compensating harmonic components

This paper proposes a voltage source converter (VSC) control strategy for the high voltage direct current (HVDC) transmission systems compensating the harmonic components. For VSC-HVDC AC system accounted for a relatively large share of the 5th, 7th, 11th, 13th and other low harmonics. A selective harmonic current control strategy based on vector proportional integral (VPI) regulator in dq coordinate system is proposed on the basis of PI control. In which, PI is used to control the DC component of the current error, while VPI is used to suppress the multiplicative fluctuations of the current error. Unlike the proportional-integral resonant (PIR) regulator, the VPI contains a second-order numerator that achieves the ideal 0° phase delay of the closed-loop transfer function of the control system at the set resonant frequency point, so its control accuracy for harmonic currents is better than that of the PIR. A two-terminal VSC-HVDC system is built using Simulink software, and current compensation simulations are performed for three control methods: conventional PI, PIR and PI parallel VPI schemes. The superior harmonic suppression performance of VPI is verified by comparing the harmonic content.

Research on Low-Frequency Stability under Emergency Power Supply Scheme of Photovoltaic and Battery Access Railway Traction Power Supply System

Photovoltaics and batteries can be connected to a traction power supply system through a railway power conditioner (RPC) to switch between different control strategies. This can address power quality issues or provide emergency traction for locomotives that unexpectedly lose power and even break through traditional energy barriers in the railway field, achieving a low-carbon power supply for railway energy, and a mutual backup with substations. However, methods to coordinate the control strategies of PV and the battery locomotive traction have not been clearly revealed, nor has the actual stability of the system. In this study, to address the above issues, an emergency power supply scheme is proposed for the first time that utilizes a dual-mode RPC inverter combined with a coordinated control strategy for the PV and battery, achieving the traction of locomotives. In addition, a one-dimensional impedance model was established for the PV system, battery system, locomotive (CRH3), and RPC projected onto the dq coordinate system, and the critical amplitude margin (CAM) was defined to quantitatively analyze the sensitivity and laws of different parameters concerning the low-frequency stability of the system. At the same time, impedance ratios and passive criteria were used to reveal the stability mechanism, and parameter adjustment criteria and design suggestions were put forward. Finally, the feasibility of the emergency power supply scheme of the “PV–battery locomotive network” coupling system and the correctness of the low-frequency stability study were verified using the Starsim semi-physical experiment platform.

Robust control strategy of VSC-HVDC systems based on feedback linearization and disturbance compensation method

The Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) technology has become the development direction of new energy grid-connected, DC power transmission and island power supply technology in the future due to its superior characteristics. The effective and reliable control method is important to realize the stable operation of VSC-HVDC system during disturbances. However, the common adopted control scheme for VSC-HVDC system lacks of superior dynamic response when system suffers external disturbances. Although some relatively new control methods have been continuously proposed and applied to the VSC-HVDC system, such as no-beat control, fuzzy control, sliding mode control and repetitive control, etc., they usually depend on detailed and exact system model. This paper focuses on the feedback linearization and disturbance compensation methods in VSC-HVDC system. Firstly, the mathematical model of VSC-HVDC system in dq coordinate system with modeling errors and external disturbances is derived. Secondly, in order to improve the dynamic response and robustness of the control, the feedback linearization and disturbance compensation method is used and designed to realize the decoupling control of the VSC-HVDC system. Finally, the VSC-HVDC system with conventional control and the proposed control is compared and analyzed on the PSCAD/EMTDC simulation platform. The results show that the proposed controller based on feedback linearization and disturbance compensation principle has better dynamic performance and higher robustness of regulation performance.

Modeling and Cooperative Control of Segmented Long Primary Double-Sided Linear Induction Motor

In this article, a novel unit motor mathematical model (UMMM) of segmented long primary double-sided linear induction motor (LP-DSLIM) is established and a cooperative control strategy for segmented LP-DSLIM fed by one inverter is proposed. First, the conventional UMMM is theoretically analyzed. Then, a virtual secondary is introduced aiming at accurately describing the secondary current when secondary passes through the primary segments. To acquire the secondary and primary flux linkage with different coupling lengths, the secondary resistance, secondary inductance, and mutual inductance are modified by using the coupling factor. According to the established UMMM, a cooperative control strategy for segmented LP-DSLIM fed by one inverter is developed. It is that the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis of the synchronous dq coordinate system is oriented to the total secondary flux linkage, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis components of the weighted primary current control the total secondary flux linkage and thrust. The effectiveness of the proposed UMMM and cooperative control strategy is validated by simulation and experiment.

PI velocity control of brushless DC motors using the extended dq transformation

AbstractThis paper is concerned with velocity control in brushless direct current (BLDC) motors. Our control scheme is composed of a classical proportional–integral velocity controller and a proportional electric current controller computed in the extended dq coordinate system. We employ a finite time estimator that has been previously proposed in the literature intended to estimate the unknown back electromotive forces. This estimator has been proven previously to converge locally to the true values. This control strategy is proposed to eliminate torque ripple produced by the fact that back electromotive forces in BLDC motors are nonsinusoidal. We present, for the first time, a formal stability result for this control scheme: (a) the state has an ultimate bound provided that the estimate of the back electromotive forces is close to the true values, and (b) this ultimate bound can be rendered arbitrarily small when the estimate of the back electromotive forces converges to the true values. This result stands when starting from any initial condition such that the finite time estimator is ensured to converge to the true values. We verify our findings through simulations.

The Stability Criterion and Stability Analysis of Three-Phase Grid-Connected Rectifier System Based on Gerschgorin Circle Theorem

With the increasing maturity of new energy technologies, distributed power systems have been widely used in the field of new energy power generation. The grid-connected rectifier is an important device in the distributed power system. When the grid-connected rectifier operates in a weak power grid environment, its operating performance deviates from the design value, endangering the operation safety of the power system. In this paper, the small-signal impedance model of the three-phase LCL grid-connected rectifier in the DQ coordinate system is established. This model considers the influence of the phase-locked loop on the rectifier impedance characteristics and improves the accuracy of the model, and on this basis, the theoretical stability of the system is analyzed. The stability judgment of the system has important engineering guidance significance. The traditional generalized Nyquist stability criterion requires a lot of calculations and is difficult to use. Therefore, a system stability criterion based on the Gerschgorin circle theorem is proposed, which reduces the amount of calculation and provides a higher size for the system design. The simulation results are consistent with the theoretical analysis, which verifies the correctness of the method proposed in this paper.

Research on STATCOM control strategy of Cascaded H-bridge considering unbalanced conditions

STATCOM, a star cascade H bridge, usually uses zero-sequence voltage injection to achieve inter-phase DC voltage balance. Different from negative sequence current injection, the phase-to-phase DC voltage balance control based on zero sequence voltage injection does not generate zero sequence current in three-phase and three-wire systems, which is beneficial to the power quality of the system. In the traditional control algorithm, the zero sequence voltage is calculated by the unbalanced active power and current. The control algorithm contains a large number of complex operations and matrix operations, which need to consume a lot of controller resources and is not conducive to system design and expansion. Moreover, in order to improve the dynamic performance under voltage imbalance, the positive and negative sequence separation is introduced into the feedforward control to increase the complexity of the control algorithm. In order to simplify the control algorithm, a PI regulator is proposed to linearly adjust the DC component of zero sequence voltage in DQ coordinate system. At the same time, through theoretical analysis, it is found that the zero-sequence voltage in feedforward control is equal to the zero-sequence voltage in power grid, so the positive and negative sequence separation can be removed, further simplifying the algorithm.

Using of a single-phase synchronous multi-winding generator with permanent magnets for the power supply of an autonomous consumer

THE PURPOSE. Consider the existing ways of using electromechanical converters for power supply of an autonomous consumer. Conduct a comparative analysis of electromechanical converters, scenarios and conditions for their use in the power supply of an autonomous consumer. To develop a proposal to eliminate the shortcomings in existing models of synchronous generators in order to increase their controllability. To develop a mathematical description of a synchronous generator with magnetoelectric excitation from permanent magnets of a single-phase type with a simplified design as a universal example of the functioning of the entire proposed line of synchronous generators. Carry out mathematical modeling of the generator proposed for consideration in order to confirm the proposed method of regulating the generated parameters, such as current and voltage, without the need to change the generator shaft rotation speed.METHODS. When solving the problem, the method of describing an electric machine in a dq-coordinate system using a multi-winding description of the machine was used; to confirm the proposed control method, mathematical modeling with the SimInTech environment was used.RESULTS. The article describes the relevance of the topic, considers the features of the operation of various electromechanical converters for power supply of an autonomous consumer, indicates the conditions for the use of one type or another of the architects of the power supply system in conjunction with electromechanical converters. A line of synchronous generators with magnetoelectric excitation is proposed in order to improve their controllability, namely, the ability to regulate the output generated parameters.CONCLUSION. Using of the proposed synchronous generators with excitation from permanent magnets will allow for additional regulation of the generated parameters, thereby allowing either completely or partially to exclude additional semiconductor converting equipment, thereby reducing losses during the conversion of electrical energy. Moreover, it is possible to regulate the generated current and voltage discretely by two times increasing one of these values, this method of regulation depends on the design of the generator.

Modellation and simulation of shunt active power filters type for variable nonlinear load

The paper is dealing with modelling and simulation of running principle of shunt type active power filter. It is possible to highlight the running of the active filter as a result of correlation of power supply voltage, the power outage on filter coil and converter input voltage. The mathematical equations for filter running were implemented into the PSIM software, both with instantaneous variables without DC voltage control and Vdc voltage control in the (dq) coordinate system. The numerical simulations performed without DC voltage control have shown a Vdc voltage overgrown. Vdc voltage control is taking off this inconvenience and allows harmonics balance putting in a filter current in phase opposition with the harmonic current of nonlinear load. By numerical simulation of varable voltage power supply of the nonlinear customer it was highlighted existence of an optimal area of THDi thanks to correlation between grid voltage, coil and converter input voltage. Choosing and dimensioning of three phase coil of power circuit of SAPF has a decisive influence on the voltage range of adjustment of nonlinear customer and implicit on THDi grid current.

Grey‐prediction‐based double model predictive control strategy for the speed and current control of permanent magnet synchronous motor

AbstractTo solve the problems of slow response speed of the permanent magnet synchronous motor (PMSM) system when the external disturbance occurs and the poor disturbance rejection performance, a double model predictive control (MPC) strategy for PMSM to control speed and current is proposed in this paper. Further, in order to improve the dynamic performance and disturbance rejection performance of PMSM control system, a grey prediction is introduced, and then a grey‐prediction‐based double MPC strategy is proposed. To be specific, firstly, the mathematical model of PMSM is established under the dq coordinate system, and the traditional control strategy (outer speed loop PI controller and inner current loop deadbeat prediction controller) is elaborated. Secondly, we propose the double MPC strategy where MPC controller is used in the outer speed loop and deadbeat prediction controller is used in the inner current loop. Finally, the grey‐prediction‐based double MPC strategy is proposed where MPC is combined with grey prediction to improve the dynamic performance in the inner current loop. By comparing the traditional control strategy with the double MPC and the grey‐prediction‐based double MPC strategy, the simulation results show that the double MPC and the grey‐prediction‐based double MPC system have no overshoot and the grey‐prediction‐based double MPC system has better steady‐state performance, faster dynamic response and stronger disturbance rejection performance, which proves the effectiveness of the proposed strategy.

Research and Simulation of Three-phase Vienna Rectifier Based on Feedforward Decoupling Control

This paper takes the three-phase VIENNA rectifier as the research object. Aiming at the problem that its dq-coordinate system model has strong coupling and nonlinear characteristics, which makes the design of the controller system more difficult, a control strategy based on feedforward decoupling control is proposed. First, this paper analyzes the working principle and mathematical model of the rectifier, then introduce the newly proposed control system and controller parameter design, and finally build a simulation model with PESIC software. The simulation results verify the correctness and rationality of the proposed feedforward decoupling control. The proposed control strategy can further reduce the harmonic content of AC side of the rectifier, improve the steady-state performance, and have better dynamic performance when the load power changes.

Research on PMSM Vector Control System Based on MTPA

Built-in permanent magnet synchronous motors (PMSM) are widely used in social life due to their strong load capacity and high-performance speed regulation ability. This paper derives the equation conversion of PMSM from abc coordinate system to dq coordinate system, introduces the basic principle of the Maximum Torque Per Ampere (MTPA), and builds a simulation model based on the MTPA vector control system using MATLAB/SIMULINK, analyzes the changing law of the simulated waveform.

The stability analysis of new power generation based on Ostrowski’s theorem

The parameter mismatch between the source side and the grid side of the grid-connected system of new energy generation is one of the factors affecting the stable operation of the grid connected system. In order to ensure the safe and stable operation of the system, the stability region of system parameters is worth studying. In this paper, a fast estimation method of stable region of impedance parameters for grid connected inverters is proposed. Firstly, the impedance model of grid-connected system in dq coordinate system is established based on the impedance analysis method, and the return matrix which is the main element influencing the stability is analyzed and deduced. Secondly, the bands containing eigenvalue loci of the return matrix are obtained based on Ostrowski’s theorem, and the stability of the system is judged by Nyquist stability criterion. Finally, the simulation results show that the proposed method can quickly estimate the stable region of the impedance parameters of the grid-connected inverter, which verifies the correctness of the method.

A Power De-coupling Control Strategy for MMC-HVDC System

Modular multilevel converter (MMC) has a wide range of applications in the field of HVDC. However, some of the electricity in MMC is coupled, which makes the design of control system more difficult and have a negative impact on the stable operation of the system. This paper puts forward a strategy to eliminate the coupling control, this method compensates the current cross-coupling terms of the d-axis and the q-axis in the dq coordinate system, SOGI(Second Order Generalized Integrator) and Q-PR(Quasi-PR) controller are used to accurately control the double frequency circulation in the internal unbalanced current, the coupling caused by the internal unbalance current and the sub-capacitor module voltage is compensated in the three-phase coordinate system. Finally, the simulation verification is carried out in PSCAD, which is compared with the traditional control method to verify that the proposed method can achieve complete power decoupling.

Control strategy of doubly-fed induction wind turbine

Based on the principles of DFIG, this paper establishes a DFIG model in a synchronously rotating dq coordinate system. For the grid-side control system, the vector control technology facing the grid voltage is used to realize the decoupling of DFIG active power and reactive power. The methods of feedforward compensation and PI control are used to control the rotor side of the DFIG. When the voltage drops above the low voltage ride-through operating standard curve, DFIG should not leave the grid. When the grid voltage drops below 0.9 times the standard unit value, DFIG should also provide reactive power to the grid to support the grid voltage. Since the reactive power that can be provided by the stator side is much greater than the reactive power on the rotor side, when the grid voltage drop is small, the stator side first provides reactive power to the grid. When the grid voltage drops more, the stator side and the rotor side share power to the grid to provide reactive power. Finally, using MATLAB/Simulink software to simulate DFIG, verify the effectiveness of the control strategy proposed in this paper, and lay a foundation for fault characteristic analysis.

Modeling of Nine-Switch-Converter Based on Virtual Leg and Its Application in DFIG Wind Generation System

This article proposes a doubly fed induction generator (DFIG) wind energy conversion system (WECS) based on nine-switch converter. In this article, a new concept of virtual-leg is proposed, and the equivalent mechanism between the nine-switch converter and the dual six-switch converter is first proposed. Furthermore, a mathematical model of the nine-switch converter based on the unipolar binary logic switching function is established. In order to simplify the mathematical model of the nine-switch-converter-based DFIG-WECS, the parameter mapping relationship between the nine-switch converter with loads and the nine-switch-converter-based DFIG-WECS under dq coordinate system is given. Meanwhile, the adaptive resonant proportional integral (PI) (AR-PI) current controller based on the resonant controller, the PI controller, and the adaptive genetic algorithm is applied for the DFIG wind generation system. As a result, harmonic current content, overshoot, and dynamic response speed of the nine-switch-converter-based DFIG-WECS have been significantly improved. Finally, the simulations and experimental results verify the validity and reliability of the proposed mathematical model and control algorithm.