Characterization of transient operation modes for a 3-phase controlled rectifier under open-loop predictive ride-through control

A current sharing method considering battery state of charge(SOC) for multi-module uninterruptable power supply(UPS) system is proposed. Modularized UPS system consists of a single master module and multi slave modules. A master module performs output voltage control and distributes current commands to slave modules. The current commands are generated by using the proposed current sharing algorithm to balance the SOC of each UPS module. Moreover, the UPS mode transfer time can be significantly reduced by using the predictive current control. The predictive current control method is mathematically verified by analyzing the UPS system. The validity of proposed balancing method and predictive control is verified by simulation results.

This paper proposes and substantiates the improvement of the on-board vibration control system of aircraft engines to expand the system’s functional capabilities and provide multi-class diagnostics based on multi-level processing of vibration signals. The possibility of diagnosing initial crack-like damage to the rotor shaft and impeller blade is considered, as well as the possibility of detecting such operational violations of the engine's regular modes, such as minor imbalance, ingress of small and medium-sized foreign objects, and grinding of the impeller blades. Such damages and disturbances do not lead to increased vibration of the rotary harmonics and are not detected by traditional analysis methods. For multi-class diagnostics, multi-level processing of vibration signals based on various combinations and/or sequential application of time-frequency analysis, multi-spectral analysis, and fractal analysis methods were used. This work proposes the structure of a subsystem of multi-class diagnostics as part of the standard on-board engine vibration control system in steady-state and transient operating modes, as well as algorithms for detecting initial crack-like damages of rotating elements and disturbances in standard operating modes. As diagnostic signs, the following are used: the Hurst index of the vibration signal in the region of subharmonic resonance in the transient mode (for the diagnosis of the initial transverse crack of the rotor shaft); dimension of Minkowski time-frequency spectra of vibration signals in stationary and transient modes (for diagnosing the initial crack of the impeller blade); simultaneous use of the Hurst index of samples of vibration signals and dimension of Minkowski estimates of the module of the bispectrum of vibration signals (for diagnosing violations of standard operating modes). The developed software algorithms use received and pre-processed signals from vibration and engine speed sensors, provide the determination of the mode of vibration disturbance, perform time-frequency, bispectral, and fractal analysis in the sequence determined for each diagnostic task, calculate the value of the diagnostic feature and compare it with the reference value, based on the results of the comparison, establish the appropriate diagnosis and submit it to the decision-making system. The proposed algorithms are intended for use in the corresponding blocks of the multi-class engine diagnostic subsystem.

In this paper, a comparative performance analysis of bridgeless boost and bridgeless buck converter for Uninterruptable Power Supply (UPS) is presented. The performance of UPS application in terms of their efficiency is compared between the conventional diode bridge converter and both bridgeless converters. The input supply power quality is also been analysed by applying open and closed loop control techniques to the converter. The results show that the efficiency and the input supply quality of the bridgeless converters are significantly improved. UPS using bridgeless boost converter has better performance in all aspect compared to bridgeless buck converter. Aligned with that, the closed loop controller for the converter has also improved the efficiency and PF more than the open loop controller in performing the UPS system. All the analytical work was performed using PSIM software.

Three-phase Uninterrupted Power Supply (UPS) is widely used in industrial field. The output voltage quality of three-phase UPS mainly depends on its control strategy. However, the internal uncertainty and external disturbance of three-phase UPS always affect the output of UPS. Aiming at describing the source of internal uncertainty, the influence of external disturbance and system coupling of three-phase UPS, the detailed mathematical model is firstly established. Secondly, according to the mathematical model, the designing method for three-phase UPS controller based on active-disturbance rejection controller (ADRC) method is proposed. Finally, the corresponding simulation model is constructed in Matlab/Simulink. The simulation results prove that the proposed strategy can effectively improve the output power quality of three-phase UPS.

This paper presents an improved method to generate the compensation reference currents applied to a three-phase line-interactive Uninterruptible Power Supply (UPS) system with series and parallel active power line conditioning capabilities. The reference currents are used to compensate the reactive power and to eliminate harmonic currents generated from the non-linear loads, in a three-phase, four-wire system. The control strategy is based on the synchronous reference frame (SRF) method and the implemented current SRF-based controller does not have the task of compensating negative and zero sequence components at fundamental frequency of the load currents, due to unbalanced loads or unbalance source voltage conditions. Thus, the efficiency of the three-phase UPS system is increased when it is feeding unbalanced single-phase non-linear loads because the PWM parallel converter compensates only the harmonic load currents. Three strategies, employed to generate the reference currents, are discussed, such as, the SRF conventional strategy, the SRF single-phase strategy and the improved SRF single-phase strategy. Besides, the active powers that flow through the parallel PWM converter using the three presented strategies are shown and a comparative analysis of them is made to validate the predicted theoretical results.

Uninterruptible Power Supply (UPS) is widely used in industry and electronics field in order to improve power quality. However, the distortion and interruption of output voltage will occur when UPS is applied to instantaneous impulsive load. This paper proposes a novel dynamic control strategy to resist impulsive load. When the impulsive load is imposed on UPS instantaneously, the impulsive current can be quickly sensed by the digital controller and the supplying power for the load is switched from inverter to bypass immediately. Therefore, the output voltage of UPS can be maintained uninterruptible. The proposed control strategy is verified by a 30 KVA UPS prototype.

A photovoltaic (PV) grid-connected power conditioning system with the function of uninterruptible power supply (UPS) is presented in the paper. It can not only realize photovoltaic generation, but also has full function of shunt active power filter (APF). In addition, it can act as UPS when instantly power interruption occurs. The instantaneous reactive power theory is employed in harmonics current detecting and signal synthesis algorithm of reference current. The proposed control strategy has two control modes (Grid connection mode and UPS mode) which can switch to each other automatically. A dual instantaneous loop control strategy is applied to UPS mode so as to obtain fast responses. The whole system is constructed and simulated in Matlab / Simulink environment. The power qualities under different conditions are given and compared. By analysis of the simulation results, it is shown that the proposed system is feasible and practical.

High quality online uninterruptible power supplies (UPS) are widely used in applications e.g. precision medical equipment with critical loads. This paper proposes a low-cost and high performance online UPS system. Firstly, the performance improvement of a bidirectional switch based bridgeless power factor (PFC) converter, which is regulated by a hybrid control strategy with load current feedforward is studied. Secondly, the proposed closed-loop controller integrates improved predictive current control with predictive voltage control and applies to the second-stage neutral-point-clamped (NPC) three-level inverter for low output voltage harmonics. Moreover, a push-pull dc-dc converter interfaces and boosts voltage of a 24V battery bank as the backup energy source. Considering complexity of the UPS system as well as cost reduction, we implement a multi-task decomposition method for control on a monolithic low-cost digital signal processor (DSP) embedded with Control Law Accelerator (CLA). Finally, the experimental results from a 1kVA a prototype can effectively verify validly of the theoretical analysis and design.

Dynamics and Control of Machines

In this paper, a regeneration protection solution is proposed to address the dc-link overvoltage issue and the unequal power sharing in the parallel uninterruptible power supply (UPS) systems. First, a dc-link voltage protection control strategy is proposed to protect the inverter against the excessive dc-link voltage that may trigger the protection mechanism of the UPS system. In addition, an active power-sharing control strategy by regulating the virtual resistance is proposed to solve the circulating current caused by UPS regeneration issue. Finally, the feasibility of the proposed regeneration protection solution is verified by experimental results from the parallel UPS system prototype.

This paper presents a novel control strategy using a genetic algorithm optimized fuzzy logic controller with repetitive learning action for uninterruptible power supply (UPS) inverter applications. The repetitive learning action can reduce steady-state errors and distortions caused by unknown periodic disturbances. Considering its poor dynamic response with sudden load change, the fuzzy logic controller (FLC) is introduced. The parameters for the FLC are optimized by genetic algorithm (GA) in the proposed scheme. The presented digital control scheme measure only the output voltage, decreasing the amount of sensors and the overall system cost. The control laws and design procedure of the control scheme are discussed. Simulation and experimental results for a single-phase UPS inverter controlled by a TMS320F240 DSP are presented to verify the performance of the proposed control approach under different load conditions. It proves to be a cost-effective solution for common UPS products.

This work presents a Model Predictive Control (MPC) strategy for a Voltage Source Inverter (VSI) used in a three-phase Uninterruptible Power Supply (UPS) for critical loads. An MPC using continuous variables is proposed for solving this problem and the output of the controller is used as the reference voltage to be generated by a PWM modulator. The solution of this unconstrained MPC gives rise to an explicit solution that can be computed beforehand, allowing the prediction horizon to be easily extended. Therefore, the effect of the length of the prediction horizon over the system performance is also evaluated in the paper. This study addresses how this parameter should be chosen to minimize the error between the actual and the desired output voltage. The proposed control strategy has been tested on a simulated model of a UPS supplying a three-phase resistor load. This model has been developed using MATLAB/Simulink with PSIM software. The simulation results show that proposed continuous MPC controller achieves high performance and high degree of robustness.

A large number of wind turbine generators in the large-scale offshore wind farm system poses a challenge to the wind farm control system due to the computational burden in the central control methods or the complexity of the communication network in the decentralized control strategies. A hybrid control method based on the distributed consensus control and the central model predictive control is proposed in this study to overcome the problem. Typically, the wind turbine generators in the large-scale offshore wind farm system are clustered into several groups. The consensus-based distributed reactive power coordination control is proposed to each cluster and the centralized predictive voltage control is used to manage the total reactive powers of all clusters and regulate the voltage at the point of common coupling. The gradient-descent algorithm for the optimal design of the consensus-based cluster control is presented firstly. Based on the convergence property of the consensus control, the equivalent model of the total reactive power response of each cluster is identified, which is used for the design of the centralized predictive voltage control. Eigenvalue analysis of the proposed predictive control strategy is carried out to verify the stability of the distributed and predictive control systems. The robustness of the proposed predictive controller is evaluated in the conditions of significant model errors due to the communication delay in each cluster. A comparison study with the full distributed control based on consensus algorithm is presented to demonstrate the effectiveness of the proposed control method. The feasibility of the proposed predictive controller is evaluated by the control-hardware-in-the-loop simulation using OPAL-RT Technologies. An additional comparison study in term of computation time with the central control method is also carried out. Real-time simulation results show the superior performance of the proposed hybrid method compared to the full distributed consensus controller or the central control strategies.

It is essential characteristics for uninterruptible power supply (UPS) to eliminate harmonic currents in its input current and to get unity power factor. Switched mode rectifier (SMR) with a high -frequency transformer link has promising characteristics as a AC/DC conversion circuit for UPS. It does not only eliminate harmonic currents but also provides an isolation between AC input and DC output with a small high frequency transformer. We applied the SMR for the development of UPS with capacity of 2kVA, 3kVA and 5kVA. This paper presents circuit configurations and control strategies of the SMR and the test results of the developed UPS.

Objetive: Display console is the software and hardware platform of warship and submarine control system. It's very important to strengthen the performance and improve the life of the Uninterruptible power supply (UPS) in display console . The residual capacity of UPS is a nonlinear function of voltage, discharge current, temperature and other variables. At present, there are some problems such as large measurement error and poor state prediction, what influence the battery power management system's management effectiveness. Therefore, this paper studies the estimation method of battery residual capacity based on BP Algorithm according to the principle of neural network, so as to improve the estimation accuracy of UPS residual capacity. Method: Firstly, we establish the BP neural network model consists of three layers, secondly gather UPS experimental data set, then build, train and test BP network model with LM algorithm by Matlab program language, finally gather the state of charge(SOC) training results. Result: Experimental results indicate that the method in this paper can estimate UPS SOC accurately and efficiently. Conclusion: It can satisfy the system requirements of uninterruptible power supply SOC estimation.