Discrete-Time Zero-Dynamic Control for 1500V Battery Three-Phase Inverter

In this study, an extended Lyapunov-function-based control strategy that assures global asymptotic stability is proposed for single-phase UPS inverters. The Lyapunov function is formed from the energy stored in the inductor and capacitor due to the fact that the system states converge to the equilibrium point if the total energy is continuously dissipated. It is shown analytically that the classical Lyapunov-function-based control leads to a globally asymptotically stable system at the expense of steady-state errors in the output voltage, which exist due to the lack of outer voltage loop in the control input. Therefore, an extended Lyapunov-function-based control strategy is proposed, which eliminates the steady-state error without destroying the global stability of the closed-loop system. The steady state and dynamic performance of the proposed control strategy has been tested by simulations and experiments under resistive and diode bridge rectifier loads. The results obtained from a 1-kW inverter demonstrate that the developed control strategy not only offers global stability, but also leads to good quality sinusoidal voltage with a reasonably low THD, almost zero steady-state error in the output voltage, and fast dynamic response under linear and nonlinear loads.

In this paper, a modified Lyapunov function based control strategy that assures global stability is proposed for single phase cascaded H bridge multilevel converter feeding nonlinear loads. The Lyapunov function is formed from the energy stored in the inductor and capacitor. The Lyapunov function based control strategy proposed in the literature for the single phase converter assures global stability with only output voltage and current control. But the DC link voltages of the multilevel inverter fluctuate due to the disturbances in the input and output side. Hence the Lyapunov function based control strategy is modified by including a DC link voltage control is proposed for the multilevel inverter. Detailed analysis has been conducted to verify the effectiveness of the proposed system and is compared with the conventional control strategies. A fast dynamic response and lower distortion in output voltage is obtained with the proposed strategy compared to the conventional control strategies. Simulation and experimental results from a laboratory scale prototype is demonstrated to assess the performance of the suggested control scheme.

Low-total harmonic distortion (THD) and fast dynamic response of multiphase converters are the major challenges for high-order quadrature amplitude modulation (QAM) in low-frequency (LF) communication (30–300 kHz). This article proposes a single-step trajectory model predictive control (SST-MPC) for 100 kHz lager-signal multiphase converters, which improves the dynamic performance of optimized pulse patterns (OPPs). Low THD of multiphase converters at a steady state can be achieved by OPPs, which is well applied to LF communication. SST-MPC proposed in this article takes the transient trajectory into account and designs a new transient trajectory to reduce the settling time. Meanwhile, the first step and the second step predictive output voltage can be calculated in parallel only by the first step future multilevel output voltage. Even if the ratio of the control frequency to the output frequency is low, fast dynamic response and over/undershoot-free can be achieved by SST-MPC. The computational burden of SST-MPC is similar to the traditional single-step model predictive control (SS-MPC). Simulation and experimental results are given to verify the excellent dynamic performance of SST-MPC. Compared with the settling time of the two state-of-the-art SS-MPCs, the average improvements of SST-MPC are 37.02% and 30.24%, respectively.

An H-bridge inverter with LC (inductor-capacitor) filter output allows the conversion of DC (direct current) power to AC (alternating current) power that has been used in a variety of applications, such as uninterruptible power supplies, AC motor drives, and renewable energy source systems. The fast finite-time sliding mode control (FFTSMC) features acceleration of the system state towards the equilibrium position as well as conserving insensitivity against internal parameter fluctuations as well as external load disturbances falling within the predetermined bounds. However, the FFTSMC would potentially witness chattering or steady-state errors as indefinite margins come to be exaggerated or underestimated. The chattering in the sliding mode control practice is oscillatory defective behavior. It induces inefficient operation, higher switching power losses in the transistor circuits, as well as saturated actuators, thus impairing the inverter’s output energy efficiency and raising harmonic distortion. Therefore, this paper presents the H-bridge inverter with LC filter output, which is controlled by a grey prediction fast finite-time sliding mode trajectory tracking. A more highly accurate grey prediction model based on the centered approximation methodology is deployed to vanish the chattering as well as steady-state errors. Taking into account the union of grey prediction and FFTSMC, a feedback-controlled H-bridge inverter with LC filter output allows attaining a highly efficient as well as quality sine-wave output voltage. The presented state-feedback control strategy is robust, less complex, attains more rapid convergence, and is highly accurate. The design process, computer simulation, as well as experimental results of the proposed state-feedback control strategy established that the H-bridge inverter with LC filter output has the capability to exhibit fast dynamic response time as well as good steady-state tracking behavior of the output voltage under step-loading changes and nonlinear loading conditions.

A novel digital controller for boost power factor correction converter is proposed to achieve high power factor and fast dynamic response. A method of direct duty cycle calculation is adopted to improve the power factor. The prediction module is adopted to estimate the track of the output voltage and the inductor current of next switching cycle in advance to improve the dynamic response. A multiplex successive approximation analog-to-digital converter (ADC) is designed to aim high resolution via little hardware resource. Meanwhile, a novel digital pulse width modulator (DPWM) is realized to improve the regulation linearity. The boost PFC converter with proposed digital controller based on the field programmable gate array (FPGA) has been implemented. Experimental results indicate that the proposed digital controller can achieve high power factor more than 0.98, the dynamic response under load variation is about 80ms and the output voltage overshoot is about 6%.

Novel or modified sensorless control methods, credited with fast dynamic response, better drive efficiency and short computation time are just a few of nowadays main concerns. Therefore, this paper aims to theoretically characterize and digitally investigate through comprehensive Matlab/Simulink simulations three different V/f control strategies, with correction loops. The proposed control methods are all characterized by the missing of the vector current control standard speed and current controllers and they all use the Maximum Torque per Ampere condition (MTPA); coordinate transformations are not necessary. The most important claims of these new control strategies are fast dynamic speed and torque response, low computation effort and the bypassing of initial rotor position problem. To prove the previous claims, a fractionary winding interior permanent magnet synchronous motor (IPMSM) 42Vdc prototype was made and its parameters were previously determined by standstill and load performance laboratory tests. Preliminary test results with proposed method three are available at this point.

This paper proposes a straightforward control method for voltage control of a three-phase transformer-based inverter in uninterruptible power supplies or distributed generation systems. The approach offers a dual-loop design consisting inner current control loop and outer voltage loop. Sliding mode current controller provides desired bandwidth for voltage controller which consists of a state feedback term for stabilization and resonant term for harmonic damping. The proposed scheme provides fast dynamic response and low total harmonic distortion even for high power inverters with the limitations of switching frequency and LC filter components. Experimental studies for 2KVA linear and nonlinear loads using digital signal processors validate excellent performance of the proposed method.

Alternative energy systems (AES) are becoming popular for small scale power generation. Designing the converters which transform the DC power into AC is the main development area of AES. Conventional single-phase voltage source inverter (VSI) uses buck topology which gives lower average output voltage than the input DC voltage. However, where the output voltage requirement is larger than the input DC voltage, such as uninterruptible power supply, fuel cell (FC) and photovoltaic systems, boost inverters are used. The boost inverter applied in this study consists of two boost DC-DC converters, which provides sinusoidal AC voltage output. The key drawback of the inverter lies in its control structure. In this paper, a dual loop control method is applied to ensure pure sinusoidal output voltage with fast dynamic response and low input current ripple. The input voltage of the inverter is assumed to be stable at 48 V considering commercially available FC voltage and the output voltage is regulated at 110 Vrms. In this article, the operating principle, mathematical modelling, analysis and control strategy of the boost inverter is presented. The proposed control strategy is verified with simulation using MATLAB/Simulink®. Simulation results show that the output voltage is 110 Vrms pure sinusoidal and the input current has low ripples.

This paper presents a virtual inertia frequency control (VIFC) strategy for two-stage photovoltaic (PV) systems in an islanded micro-grid. By adjusting capacitor voltage and PV output power simultaneously, sufficient energy can be guaranteed for inertia synthesis from PV systems directly. Meanwhile, primary and secondary frequency regulation can also be emulated with fast dynamic response. High performance and reliability can be ensured since all the control signals are based on local measurements and no extra phase locked loop (PLL) is needed. Analysis is confirmed via small signal models and simulation studies demonstrate the effectiveness of the proposed method.

Model-predictive current control (MPCC) is a promising candidate for modular multilevel converter (MMC) control due to its advantages of direct modeling and fast dynamic response. The conventional MPCC, which obtains the optimal control input by evaluating a cost function for all the possible switching states, may make the MPCC impractical due to the exponentially increasing computation burden with the increasing number of submodules (SMs). On the other hand, the MPCC experiences high load current and circulating current tracking errors, since only one switching state is selected and applied during one control period. To address these issues, this paper proposes an MPCC with phase-shifted pulsewidth modulation (PS-PWM) for improving the steady-state control performance. The arm voltages are considered as a whole to implement the proposed MPCC. The optimal duty cycle is obtained based on the load and circulating current tracking error minimization and applied using the PS-PWM. As a result, the computation burden is unrelated to the number of SMs by avoiding the exhaustive evaluation process for all the possible switching states. A better steady-state performance with smaller tracking errors is achieved with the similar switching frequency, and the tedious tuning process of the weighting factor is eliminated. Experimental results are presented to demonstrate the effectiveness of the proposed MPCC.

This paper proposes an improved model predictive control (MPC) scheme with a robust prediction and stability-constrained finite states for three-phase voltage source inverters ( $3\phi $ -VSIs) with an $LC$ filter. In this paper, the stability-constrained finite states are selected via the asymptotic stability conditions as a key factor to reduce the total harmonic distortions (THDs) and steady-state errors. Meanwhile, the Kalman filter-based observers improve the overall robustness against model mismatches and noises via a robust prediction. To select the stabilized finite states, the stability conditions are derived by the equivalent feedback-gains and constrained in the exhausting search of the proposed finite-set (FS) MPC. Unlike conventional FS-MPC methods, three control targets (i.e., robustness, stability, and optimality) are simultaneously achieved as the new contributions to remarkably enhance the voltage control performance of the $3\phi $ -VSI, which are also the challenge of the conventional control methods. To verify the superiority of the proposed FS-MPC, comparative studies are conducted on a prototype three-wire $3\phi $ -VSI system with a TI TMS320F28335 DSP under practical conditions (i.e., parameter mismatches, linear/nonlinear-load step-changes). The experimental results confirm that the performance of the proposed FS-MPC has been significantly improved in terms of lower THDs, smaller steady-state errors, faster dynamic response, and more robustness under critical system changes as compared with the conventional FS-MPC.

This paper presents a simplified hybrid modulation method for operating dual-active-bridge (DAB) converters that power inverters by integrating single-phase shift (SPS) and triple-phase shift (TPS) modulation schemes. It covers the design and control algorithm development, performance analysis, as well as highlights its benefits and limitations. While full TPS implementation is highly complex, this work selects a specific TPS operating mode to enhance DAB converter efficiency in low-power conditions with minimal control effort. In the proposed method, a hysteresis controller is employed to regulate the DAB modulation at a defined power threshold. This poses a significant challenge, especially when a single proportional-integral (PI) controller is employed to regulate output power with a minimal set of control parameters applicable to both modulation schemes. Moreover, in addressing these challenges, a trade-off between high efficiency and fast dynamic response is also considered, with greater emphasis placed on efficiency when developing the controllers. Meanwhile, the inverter output voltage is independently controlled regardless of the DAB operation to further simplify the overall process. Small signal modeling and closed-loop control of DAB-based inverter with the proposed hybrid modulation are also presented. Its functionality and performance have been verified through simulation and a developed small-scale DAB-based inverter prototype.

A new hybrid switching frequency technique is proposed in this paper to improve the efficiency while providing fast dynamic response. Under steady state condition, the switching frequency of resonant converter is controlled to track the resonant frequency of converter to either reduce the turn-off losses or circulating losses of converter, and thereby improving the efficiency. The output voltage regulation (or voltage gain) of resonant converter is achieved mainly by tuning the DC-bus voltage of power factor corrector. Under transient condition, the DC-bus voltage is fixed and the switching frequency is determined by the load condition to improve the transient response speed. A digital-controlled converter with power factor correction and full bridge resonant converter are build up for test and confirmation. The designed and implemented 540 W / 12 V server power is with AC input voltage of 115/230 V. Test results confirm the proposed hybrid switching frequency control provides frequency tracking under steady state and fast dynamic response under transient condition.

Efficiency optimisation is one of the critical issues concerned with the electric vehicle. It has a significant influence on the vehicle performance parameter - milage or running distance per battery charge. Modification of the existing structural design and minimising the component losses are two possible solutions. Minimising the component and its interaction losses by modifying the control strategy has less impact on the existing system architecture. Direct torque control (DTC) is often preferred for electric vehicle thanks to its fast dynamic response. However, inverter switching losses are very high in DTC. Along with this, harmonics in the inverter output increases the electric motor losses. Switching frequency reduction can help to minimise inverter losses. But reduced switching frequency pushes the lower order harmonic component of the inverter output voltage to the high-frequency side and demands increased size of the filter to be employed. These two conflicting objectives addressed with the help of finite control set-model predictive control (FCS-MPC). Simulation results of both control strategies for constant velocity and drive cycle tests confirm the effectiveness of this proposal. The performance measures ascertain a strong argument for FCS-MPC as a future electric vehicle control strategy.

The purpose of this research is to optimize control and enhance performance for a variable speed constant frequency (VSCF) doubly-fed induction generator (DFIG) wind turbine generation system by using fuzzy logic controller. The control of the rotor-side converter is realized by stator flux oriented control and the fuzzy controller performs robust speed control. The control of the grid-side converter is carried out by a control strategy based on grid voltage orientation and it is controlled to maintain the DC link voltage stability. The results obtained from a system using the proposed fuzzy controller show more accurate control performance and faster dynamic response with almost no steady state error when compared to a system using conventional PI controller. Performances have been validated in this paper.