A Fuel Cell Assisted Single-Phase Multi-Port Uninterruptible Power Supply with Finite Control Set Model Predictive Controller

This paper presents the digital control scheme of a single phase uninterruptible power supply (UPS). In order to obtain fast response in the current control, the authors propose the digital control scheme based on the instantaneous values. The inverter of the UPS is connected to the load in parallel to reduce the loss of the UPS. The controller is constructed by a DSP. The control schemes in all of the operations of the UPS are described. All operations of the UPS using the proposed control scheme have been verified by experiments.

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.

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 paper presents a nonlinear feed-forward controller applied to single-phase uninterruptible power supplies (UPS). The controller was conceived by using a one-cycle based PWM generator and an output-current feedforward, in order to cancel input-voltage disturbances and nonlinear load currents, respectively. It also includes an external control loop to ensure good output-voltage tracking. The controller design is based on a large-signal approach, introduced to achieve good transient response and stability in a wide range of parameter variations. Besides, in spite of the nonlinear nature of the controller, we obtain a linear average output-voltage dynamic response. The proposed control provides the following features: fast transient response, low THD sine-wave output-voltage, fixed switching frequency, and high robustness against load and line step changes. Simulation results show the effectiveness of this control technique for inverters in UPS applications, especially when nonlinear loads must to be supplied and UPS DC-link has large undesirable ripple.

The paper presents the single phase uninterruptible power supply (UPS) system with galvanic separated DC-AC-DC-AC converters operating in parallel. The CAN physical layer based system of communication between converters has been developed and applied, which allow to utilize a decentralized master-slave control providing high availability factor of the whole UPS system. The control system of particular converters has been developed to ensure a high quality of the output voltage for both linear and nonlinear load. The selected simulations and experimental results obtained for 5 kVA prototype modules are presented.

A power converter topology suitable for online single-phase uninterruptible power supply (UPS) systems is presented. The converter uses only four switches, five if a low-voltage battery and resonant link operation are required, to realize very desirable features. These include independent control of the input and output currents a common neutral connection, line conditioning, sinusoidal input currents independent of load current, and battery charge/discharge regulation. Detailed simulation results and experimental results are included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper presents a discrete integral sliding mode control scheme with time-delay compensation for the output voltage regulation of an uninterruptible power supply (UPS) inverter. Since the inverter is subject to the parameter variation and the load disturbance and the time delay is introduced due to the adoption of digital control scheme, the controller is required to reject the disturbance as well as the influence of the time delay. This paper analyzes and models the discrete single-phase UPS inverter with time delay. To enhance the robustness of the inverter the discrete integral sliding mode control scheme is proposed. An integral controller is added to improve the steady performance of the controller and the time-delay compensation is considered to eliminate the influence of the time delay. The inverter has shown its excellent voltage tracking performance through the simulation results and the effectiveness of the scheme is verified..

This paper proposes a finite set model predictive control (FS-MPC) based thrust maximization technique for linear induction machines used in linear metros. For modeling of the proposed control method, the end effect is taken into consideration. The proposed control method is used to achieve maximum thrust per ampere and to reduce the thrust ripples. It differs from the FS-MPC methods, where the cost function consists of the thrust and angle errors. The thrust error is calculated from the difference between the reference thrust and the predicted thrust, and the angle error is calculated from the difference between the angle of predicted primary current and the angle of the predicted secondary flux in one side and π/4 on the other side. A comparison between the proposed method and the finite set model predictive direct thrust control (FS-MPDTC) is presented to illustrate the superiority of the proposed method. Both simulation and experimental analysis are conducted to validate the effectiveness of the proposed finite set model predictive direct angle control (FS-MPDAC). A prototype test platform is developed in the laboratory with two 3 kW arc induction motors. The simulation model, experimental test platform, and test results are presented in this paper.

In this paper, the switching frequency reduction in two paralleled Uninterruptible Power Supplies (UPS) is studied in order to obtain maximum global system efficiency. Typically, by reducing the switching frequency of a converter, its efficiency increases. However, when connected in parallel, UPSs are subjected to a Zero Sequence Circulating Current (ZSCC) that compromises a correct system operation and increases the losses of the global system. Experimental results show that to achieve the maximum system efficiency, the ZSCC must be effectively eliminated. Finite Control Set Model Predictive Control (FCSMPC) is used as the control scheme.

This work introduces the control concept of variable sampling time finite control-set model predictive control (FCS-MPC). The new control concept is introduced in theory based on a review of the conventional FCS-MPC concepts performed with a constant sampling time. Based on the partitioning of the sampling instant in multiple smaller sampling instants it is possible to optimize, besides the switching states, the switching states turn-on times. Therefore, the proposed variable sampling time FCS-MPC sets both: the switching state and the related turn-on times. To utilize the available calculation power for longer sampling instants an adaptation of the control- and prediction horizon to the sampling time is proposed. The theoretical control concepts are applied to the control of a grid connected two-level voltage-source converter where a simple L-type line-filter is used to demonstrate the control performance of the variable sampling time FCS-MPC algorithms in the laboratory environment.

In this paper, a Lyaupnov-based finite control set model predictive direct torque control for the permanent magnet synchronous machine (PMSM) is proposed. In the proposed control scheme, the finite control set prediction and the Lyapunov theory are combined to minimize the torque ripple. The eight voltage vectors of the two-level converter are utilized as a finite control set for the torque prediction of the PMSM. A cost function considering the torque error, the maximum torque per ampere operation and the current limitation is introduced. Comparing to the conventional finite control set predictive control, the dominant part of the cost function is utilized as a Lyapunov function to estimate the duty cycle of each voltage vector. An optimum voltage can be obtained by the optimum voltage vector from the eight vectors and their duty cycles. A small sampling frequency and a fixed switching frequency can be realized when compared to the conventional finite set model predictive control. In the end, the simulation and experimental results validate the performance of the proposed control scheme.

A direct torque control (DTC) with a modified finite set model predictive strategy is proposed in this paper. The eight voltage space vectors of two-level inverters are taken as the finite control set and applied to the model predictive direct torque control of a permanent magnet synchronous motor (PMSM). The duty cycle of each voltage vector in the finite set can be estimated by a cost function, which is designed based on factors including the torque error, maximum torque per ampere (MTPA), and stator current constraints. Lyapunov control theory is introduced in the determination of the weight coefficients of the cost function to guarantee stability, and thus the optimal voltage vector reference value of the inverter is obtained. Compared with the conventional finite control set model predictive control (FCS-MPC) method, the torque ripple is reduced and the robustness of the system is clearly improved. Finally, the simulation and experimental results verify the effectiveness of the proposed control scheme.

This Paper evaluates the integration of fuel cell power system with the grid using finite control set model predictive controller. A mathematical model of the phosphoric acid fuel cell power system is designed. The grid and the fuel cell are modeled in PSCAD simulation environment. Direct power control technique for model predictive controller is used to control the converter. The steady state results are shown in the paper, Also, a single phase fault and three phase fault is applied at the grid side to study the effect of integrating the fuel cell with the grid. The simulation results show model predictive controller can effectively integrate fuel cell with the grid.

The active and reactive load distribution between n paralleled single-phase uninterruptible power supply (UPS) inverters is equalized by virtue of n-1 load-sharing control loops. The approach permits the construction of UPS systems of any desired power rating at maximum utilization of the power components. The method of harmonic cancellation decreases the switching frequency of the power devices while maintaining good dynamic performance. The design details of a 45 kVA UPS inverter system with 150% steady-state overload capability are presented. The performance under various operating conditions is illustrated by oscillograms.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Deadbeat control (DBC) has been known for decades due to its conceptual simplicity and good performance. Recently finite control set model predictive control (FCS-MPC) is emerging as a powerful strategy for control of power converters. Different from DBC, which uses a modulator such as space vector modulation (SVM), FCS-MPC directly obtained the optimal switching states of power converters by minimizing a cost function. Several improved versions of FCS-MPC have been proposed to improve the steady state performance by introducing two or three vectors during one control period. This paper investigates the inherent relationship between SVM-DBC and multiple-vector FCS-MPC. It is found that with the aim of tracking error minimization, the two kinds of predictive methods can be unified in one frame, where the vector sequence and duration in FCS-MPC can be easily obtained from SVM-DBC. In other words, under some special cases, FCS-MPC and its improved versions can be considered as special cases of SVM-DBC. This is the main contribution of this paper, because DBC and FCS-MPC are previously studied separately. The theoretical study is confirmed by the analysis on state-of-the-art DBC and FCS-MPC and supported by the selected simulation study and experimental tests from a three-phase two-level voltage source PWM rectifier.