Control Of Synchronous Machines Research Articles

Photovoltaic Power Injection Control Based on a Virtual Synchronous Machine Strategy.

The increasing participation of photovoltaic sources in power grids presents the challenge of enhancing power quality, which is affected by the intrinsic characteristics of these sources, such as variability and lack of inertia. This power quality degradation mainly generates variations in both voltage magnitude and frequency, which are more pronounced in microgrids. In fact, the magnitude problem is particularly present in the distribution systems, where photovoltaic sources are spread along the grid. Due to the power converter's lack of inertia, frequency problems can be seen throughout the network. Grid-forming control strategies in photovoltaic systems have been proposed to address these problems, although most proposed solutions involve either a direct voltage source or energy storage systems, thereby increasing costs. In this paper, a photovoltaic injection system is designed with a virtual synchronous machine control strategy to provide voltage and frequency support to the grid. The maximum power point tracking algorithm is adapted to provide the direct voltage reference and inject active power according to the droop frequency control. The control strategy is validated through simulations and key experimental setup tests. The results demonstrate that it is possible to inject photovoltaic power and provide voltage and frequency support.

Fault tolerant control of permanent magnet synchronous motor based on hybrid control strategies DTC-SVM with second order sliding mode control using multi-variable filter

This paper describes direct torque control (DTC) of a permanent magnet synchronous machine (PMSM) powered by a two-level voltage inverter whose switching of switches is based on the Space Vector Modulation. To overcome the robustness of the control to the presence of a fault, we included an improvement of the direct torque control with Space vector modulation (DTC-SVM) by the use of the filters for the flux and the torque and compared to the direct torque control of the DTC-SVM, the PI controllers are replaced with sliding mode blocks, This control method allows giving a new structure DTC -SVM with sliding mode control. The analysis of the results shows good performances for the speed and a considerable reduction of the fluctuations at the level of the torque and the flux.

Adaptive low voltage crossing strategy for symmetrical faults of networked inverters

Abstract Due to the inability of grid-following control methods to compensate for the comprehensive reduction in system inertia, strength, and short-circuit capacity caused by the decreased proportion of synchronous machines, the grid exhibits insufficient resilience to disturbances, leading to severe stability risks in terms of rotor angle, frequency, and voltage. Grid-forming inverters have emerged to address this issue. During symmetrical faults, the low-voltage ride-through of grid-forming inverters often involves freezing the reactive power loop, resulting in a direct output of higher voltage and reactive current. However, an increase in reactive power command leads to a sharp rise in the internal potential magnitude of grid-forming inverters. Upon clearance of the grid fault, the excessively high internal potential may cause a rapid, short-term increase in terminal voltage, potentially resulting in overvoltage, which is detrimental to the operation of grid-connected equipment. In response to this issue, this paper proposes an adaptive low-voltage ride-through control strategy for grid-forming inverters under symmetrical faults controlled by a virtual synchronous machine control method. Initially, a virtual synchronous machine control model is established. Limiting current is achieved through the construction of a fixed virtual impedance loop. The issues associated with fixed virtual impedance current limiting are analyzed, leading to the proposal of an adaptive virtual impedance control strategy. Finally, the feasibility of the proposed method is verified through simulation experiments.

Optimal control strategies for PMSM with a decoupling super twisting SMC and inductance estimation in the presence of saturation

This paper deals with optimal control strategies robustified by a decoupling super-twisting sliding mode control (ST-SMC) for permanent magnet synchronous machines (PMSM). In general, ST-SMC is a robust method for controlling systems and guarantees asymptotic convergence in cases where the upper bound of model uncertainties such as disturbances and parametric uncertainties is not known a priori, if the upper bound of the derivative is known. The proposed optimal control strategy is designed for a constant torque reference whose control is implemented in two control regions: maximum torque per ampere (MTPA) and flux-weakening control. In the proposed analysis, the operating point of the motor can also be in the saturation region, which makes the estimation of Ld and Lq in the proposed optimization procedure of particular interest and also important for the decoupling control implemented with ST-SMC. To compensate for typical parameter variations, adaptive parameter estimation is introduced into the control system using an extended Kalman filter (EKF) in combination with a bivariate polynomial. In order to be able to make an assessment of the control performance of the ST-SMC, a comparison with a conventional PI controller is shown at the end of the paper. Measured results using hardware in the loop (HIL) to validate the results and their detailed discussion and analysis are included.

Confidence Weighted Learning Entropy for Fault-Tolerant Control of a PMSM With a High-Resolution Hall Encoder

There are several non-idealities that can degrade magnetic Hall-effect sensors performance and impact related applications. Thus, a confidence weighted learning entropy (CWLE) is proposed as a fault-tolerant control strategy for field-oriented control (FOC) of permanent magnet synchronous machines (PMSM). It combines sensorless and sensor-based control, while capitalizing on their major advantages, such as operation from standstill and at lower speeds, fast dynamic response, and fault tolerance to encoder errors. Encoder fault detection is based on learning entropy, that monitors weights increments of two predictive filters of angular displacement. If the two observed systems behave similarly, the variance of the weights increments is similar. A higher variance, on the other hand, reflects unforeseen misbehavior of a particular system, leading to a decrease in its confidence. A voting mechanism based on confidence weighted average then decides which of the two systems should be used for FOC of PMSM. The method has been experimentally verified on a high-speed PMSM, achieving more reliable control performance with fast response to encoder failures.

Double star permanent magnet synchronous machine: modified direct torque control

In the area of high power drives, double star synchronous machines are an interesting choice compared to conventional synchronous machines, due to the relatively low torque ripple created. In this paper, direct torque control (DTC) of double star permanent magnet synchronous machine (DS-PMSM) using artificial neural networks (ANN) is proposed. MATLAB/Simulink results show the comparison between direct torque control (DTC) and direct torque control using artificial neural networks (ANN). The analysis of the results shows good performance for speed, small torque and flow ripple when using the artificial neural network (ANN) strategy.

Open-Circuit Fault-Tolerant Control for Pentagon Winding Connected Five-Phase Current-Source Inverter Based PMSM Drives

Current-source inverter (CSI) is considered as a prospective solution for modern machine drives, for its higher reliability and superior harmonic suppression. The open-circuit fault-tolerant control for five-phase CSI-fed permanent magnet synchronous machine (PMSM) drive with pentagon winding connection is investigated. The switch open-circuit fault and winding open-circuit fault are studied. For the switch open fault, three cases are discussed including single-phase, adjacent two-phase, and nonadjacent two-phase faults. It is indicated that in pentagon circuit, despite the switch of fault phase is disabled, the corresponding phase winding is still connected in the end-to-end power circuit and contributes for torque generation. The new sets of coordinate transformation are proposed, and the mathematical modeling is presented. The fault-tolerant space vector modulation (SVM) techniques are proposed based on the reconstructed vector planes. In addition, the single winding open fault is studied, which is a specific fault case and breaks off the closed pentagon connection. An important conclusion is derived that the pentagon winding connected CSI (PWC-CSI) gains inherent fault-tolerant capability against the single winding open circuit. The control algorithm even does not need to be switched during this typical fault. Experiments are performed on verifying the proposed schemes.

A data‐driven identification method for impedance stability analysis of inverter‐based resources

AbstractObtaining inverter controller information may be a premise for seeking its dynamic behaviour. But accurate knowledge of such information would be unrealistic for real functioning inverter‐interfaced generators (IIGs), which hinders the stability analysis of the IIG. A new data‐driven impedance identification method is proposed for stability analysis, which involves an improved sparse identification algorithm as an ancillary function within the system identification framework. It contains mainly two design stages. First, the transform basis matrix (TBM) is devised systematically as a prior knowledge library to contain the possibly existing control structures. In the second stage, a sparse identification algorithm is reformulated in order to extract the relevant structures in TBM while obtaining controller parameters. The authors demonstrate that the sparse vector between the TBM and output signal is closely related to the controller structure. The effectiveness of the proposed method is verified on grid‐connected inverters based on droop control and virtual synchronous machine control.

Fixed Switching Frequency Direct Model Predictive Control of Synchronous Reluctance Machines Based on Stator Flux Gradients

Fixed Switching Frequency Direct Model Predictive Control of Synchronous Reluctance Machines Based on Stator Flux Gradients

Simplified Loss Minimization Control for Interior Permanent Magnet Synchronous Machine Based on Virtual Current Signal

Simplified Loss Minimization Control for Interior Permanent Magnet Synchronous Machine Based on Virtual Current Signal

Multiobjective Hyperparameter Optimization of Artificial Neural Networks for Optimal Feedforward Torque Control of Synchronous Machines

Multiobjective Hyperparameter Optimization of Artificial Neural Networks for Optimal Feedforward Torque Control of Synchronous Machines

Virtual Synchronous Machine Control for Doubly Fed Induction Machine-Based Wind Energy Conversion Systems

Virtual Synchronous Machine Control for Doubly Fed Induction Machine-Based Wind Energy Conversion Systems

Improved performance and robustness of synchronous reluctance machine control using an advanced sliding mode and direct vector control

AbstractThis article focuses on improving the control approach for a synchronous reluctance motor (SynRM) drive powered by a two‐level pulse width modulation (PWM) inverter. While classical sliding mode control (SMC) has been extensively used in control system design, it comes with various drawbacks such as pronounced chattering effects, considerable transient state errors, and reduced robustness. These limitations hinder its practical applicability. To enhance the performance of the SynRM, this paper introduces a novel strategy that combines direct vector control (DVC) with advanced sliding mode control (ASMC), here referring to third‐order sliding mode command (TOSMC), for regulating speed and dq‐axis stator currents. The primary objective of this approach is to achieve precise and efficient control while minimizing total harmonic distortion (THD) in current and reducing output torque fluctuations. Notably, this strategy capitalizes on the strengths of TOSMC and DVC. The efficacy of the proposed control scheme is verified through two sets of thorough simulations realized in MATLAB/Simulink environment. The first set of simulations encompasses the load–torque test, where the motor is subjected to two different levels of load torque. The results from these tests showcase the control scheme's performance under varying load conditions. The second set of simulations involves the speed variation test, where intentional changes are applied to the motor's speed. This test assesses the control approach's ability to handle dynamic speed changes effectively. The proposed control strategy is further compared with conventional control methods, including proportional–integral and second‐order sliding mode command (SOSMC) controls. The results consistently demonstrate the superior performance of the novel approach in terms of accurate control, robustness, and overall stability. The combination of DVC and TOSMC offers a promising avenue for achieving enhanced motor control in the presence of load disturbances and speed variations.

Current Harmonics and Unbalance Suppression of Dual Three-Phase PMSM Based on Adaptive Linear Neuron Controller

A strategy of current harmonics and unbalance suppression based on the vector space decomposition control with adaptive linear neuron (ALN) controller for the dual three-phase permanent magnet synchronous machine (DTP-PMSM) drive system is proposed in this paper. According to the conventional vector space decomposition theory, the compensation voltages from the ALN controller in the dq-frame and dqz-frame are employed to suppress the 5th and 7th current harmonics and unbalances. Compared with the VSD control using only the PI controller, the current harmonics and unbalance are sufficiently suppressed in the proposed strategy. In addition, unlike the resonant controller discretized by conventional Tustin transformation, the ALN controller has no resonant pole shift to the desired resonant frequency. Therefore, the harmonic suppression effect of the proposed strategy exhibits better performance than the VSD control with the resonant controller, especially in the high-speed region. Finally, the feasibility and effectiveness of the proposed strategy are validated by experimental results under both steady and transient states.

A Quasi Edge Aligned Pulse-Width Modulation to Enhance Low-Speed Sensorless Control of PMSMs With a Single DC-Bus Current Sensor

The low-speed sensorless control of permanent magnet synchronous machines (PMSMs) with a single DC-bus current sensor has not been solved thoroughly from the prior literatures. This article proposes a novel quasi edge aligned pulse-width modulation (QEAPWM) to realize this purpose. Compared with the conventional phase-shifting PWM, the QEAPWM has several advantages of the accurate reconstructed phase-current and the fixed current sampling time interval, which are beneficial to obtain the current ripple evoked by the high-frequency (HF) injected voltage to estimate rotor position. The effectiveness of the proposed method is verified on a 500-W PMSM drive and compared with three state-of-the-art methods. The experimental results verify that the QEAPWM-based sensorless control achieves satisfactory performance both in the transient and steady-state processes with the maximum 15° position estimation error without a magnetic cross-coupling saturation compensation, and nearly zero error with this compensation.

Parameter Optimization of Energy Storage Virtual Synchronous Machine Based on Particle Swarm Optimization Algorithm

Energy transformation is a severe challenge and major demand faced by China’s sustainable development, and new energy development has become a key driving force for energy transformation. The issue of system stability is brought to light by the steadily rising share of renewable energy sources like wind and solar, which in turn places greater demands on the inertia support capacity of power plants. In order to replicate the dynamic equations of a conventional synchronous machine and add inertia and damping to the system, a new technology known as virtual synchronous machine (VSM) control has arisen. Therefore, improving the system’s absorption capacity of new energy generation and ensuring its safe and stable operation are both greatly aided by the study of energy storage VSM control technology’s grid stability and parameter design methods. Although VSM control adds inertia to a system, which is good for stability, it also complicates the system’s ability to withstand tiny disturbances. This paper investigates the small disturbance stability of VSM-controlled power generating and storage systems. The stability analysis method of storage VSM when subjected to random power sources is investigated further, and a method for optimising the system’s parameters is proposed. VSM with optimised parameters can provide sufficient inertia and damping under complex operating conditions, as shown by simulation results in real-world systems. Finally, the proposed method’s efficacy was assessed with the help of an enhanced binary particle swarm optimisation (EBPSO) algorithm, and the outcomes confirmed its superiority.

Sensorless Control of Wound Field Synchronous Machine Drive Using Current Source-Based Modular Multilevel Converter

This paper proposes a wound field synchronous machine (WFSM) drive using a double star chopper cell (DSCC) based modular multilevel converter (MMC) for high power medium voltage variable speed applications. A controlled current source delivers power to this DSCC-MMC. This current source is derived using the field winding of WFSM and a 12-pulse full-controlled thyristor rectifier. The 12-pulse rectifier draws power from a three-phase grid and delivers power to the field winding and the DSCC-MMC. Thus, the field current of WFSM becomes the input dc current of the DSCC-MMC, and no separate power supply is required for the field winding of WFSM. The input current to the DSCC-MMC is kept constant at all operating speeds of the WFSM for a given value of torque to keep peak-peak voltage ripple constant across the submodule capacitor of the MMC. The field current is varied proportionately with the average torque to avoid the saturation of the machine at light load torque. This variation of field current is essential for the successful operation of DSCC-MMC. The small current ripple in the field current, caused by the 12-pulse thyristor rectifier, is utilized to extract the rotor speed information for sensorless operation of vector-controlled WFSM drive. Simulation results are presented in this paper to verify the proposed configuration and their control strategy at medium voltage. A hardware prototype has also been built in the laboratory to verify the same results experimentally at low voltage and low power.

A Closed-Loop PMSM Sensorless Control Based on the Machine Acoustic Noise

In this paper, a novel sensorless control for Permanent Magnet Synchronous Machine (PMSM) using its radiated acoustic noise is proposed in which a high-frequency voltage signal is superimposed upon the fundamental excitation and the machine response to such excitation is studied. Firstly, the analytical equations describing the field formation within the airgap leading to the generation of radial forces and acoustic noise are extensively investigated. In the next step, resulting harmonics in the acoustic noise waveform caused by the injected signals are predicted. Then it is experimentally verified that, depending on the machine structure, there will be some distinctive sidebands around the injected frequency directly related to the fundamental synchronous frequency. Acoustic noise waveform is highly distorted and sensitive to the environment, so a proposed 4-stage signal processing algorithm containing two self-adaptive Band-pass Filters (BPF) are used to safeguard the signal against unwanted distortions and flawlessly extract the rotor position information. Robustness and effectivity of this method is verified experimentally in various operating conditions.

Transient Stability Enhancement Strategy for Islanded Microgrids Based on Energy Storage–Virtual Synchronous Machine Control

In a high percentage of new energy-islanded microgrids, the overall inertia of the system gradually decreases, and the transient stability requirements of the microgrid frequency and voltage become more and more demanding under low-inertia conditions. To improve the transient stability of low-inertia islanded microgrid frequencies and voltages, this paper proposes a transient stability enhancement strategy for islanded microgrids based on energy storage system (ESS)–virtual synchronous generator (VSG) control. Model predictive control (MPC) is added within the active control loop of the VSG to achieve dynamic correction of the active power reference value of the VSG; PI control link is added within the reactive control loop to achieve a fast dynamic response of the reactive power command value. The ESS achieves fast and accurate regulation of frequency and voltage according to the power reference value of the VSG active control loop and the power command value of the reactive control loop simultaneously. Considering the need to ensure the ability of VSG to operate stably during transients, a comprehensive current-limiting technique combining virtual impedance and phase limiting is used to limit the fault current of VSG and maintain its synchronization and stability. Finally, the simulation results verify the strategy’s effectiveness and the superiority of the transient stability enhancement effect.

Finite-Time Control for Dual Three-Phase Hybrid Excitation Synchronous Machine Based on Torque Sensorless Current Coordinative Strategy

In this paper, the finite time speed regulation problem is investigated for a dual three-phase hybrid excitation synchronous machine (DTP-HESM) without a torque meter. The electromagnetic torque estimation required in the current coordinative strategy is obtained through the disturbance estimation technology. This method increases fault tolerance and reduces the cost as well as complexity of the DTP-HESM system. In contrast to the existing controllers in the speed loop, the non-singular terminal sliding mode control method is adopted to ensure the finite-time convergence of speed tracking in the whole speed region. To achieve better dynamic performance in the presence of lumped disturbances, including unknown load torque and unmodeled dynamics, the disturbance estimations are introduced into the sliding mode variable to establish a composite speed regulating controller. Simulations and experiments are carried out to validate the feasibility and effectiveness of the proposed control scheme.