Rijil Ramchand

Single-stage inverters are gaining more attention nowadays due to its lesser power conversion stage, which will improve the efficiency. Conventional single-stage inverters are buck-boost derived types, which have the drawbacks of low voltage gain and discontinuous DC input current. Also, to boost the voltage level in single-stage inverters, step-up transformers or coupled inductors are used, which will make the system bulky. So, in this paper, a novel high-gain switched capacitor single-stage inverter is proposed which will utilize only one inductor and a single DC source which is shared in both positive and negative halves of the output AC voltage. This sharing will eliminate mismatch and asymmetry in the AC waveform. Since the duty cycle of the proposed inverter varies in each switching cycle, the linearized state-space averaged model deviates from its performance. To overcome this constraint, a novel low frequency average based model is proposed in this work. A comprehensive mathematical analysis of the proposed inverter is validated with MATLAB simulation and hardware prototype.

DC-bias current flowing in the high-frequency transformer (HFT) of a voltage-regulated dual active bridge (DAB) dc–dc converter during the transient conditions can cause magnetic saturation. Considering the wide acceptability of DAB converters in different applications, the dc bias current flow in HFT should be curtailed. A unified control strategy aiming for effective voltage regulation at the load-side and mitigation of dc-bias current during the transient operation is essential. This article proposes two control strategies based on asymmetric-modulated current-averaged predictive control (AMCPC) to improve the transient dynamics of the converter by eliminating the flow of dc-bias current through HFT along with voltage regulation. The proposed predictive control approaches introduce additional term to the cost function to ensure zero average value of HFT current. An asymmetric modulation scheme is implemented by updating the phase shift ratio twice in a switching cycle to reduce the transient duration. The control logic makes sure of fixed-frequency operation, ensuring effective passive component design. The dominance of the proposed control algorithms is validated through simulation and experimental results.

The modulation techniques of dual active bridge dc–dc converter with higher degrees of freedom give opportunities for optimization. This article investigates the effect of three existing optimization strategies that aim at minimizing current stress, backflow power, and reactive power delivered by the leading H-bridge terminal of the converter. The study leads to proposing a novel optimization strategy to simultaneously achieve multiple objectives, while ensuring reduced complexity in the control algorithm. The proposed strategy aims to minimize the reactive power seen by the equivalent leakage inductance of the high-frequency transformer, which is the difference in reactive power delivered by the leading and lagging H-bridge terminals of the converter. The steady-state performance of the converter is improved by attaining zero voltage switching for all the switches in a wider power range with reduced backflow power and current stress. Experimental results are presented to validate the theoretical analysis and effectiveness of the proposed optimization strategy.

Due to the factors such as high efficiency, power density and excellent torque speed characteristics, PMSM is being widely used in Electric Vehicles and other industrial applications. Hence, a lot of research works are going on to improves its control strategies. PMSM being costlier than induction motor, this paper focuses on quicker and real time fault detection of the inverters used with PMSM so that it prevents further damage to the motor as well to the users. Several methods such as signal based and data-based methods are already in discussion for the fault detections. Inverters being the main component of the system, faster fault identification methods in real time systems are necessary. Also identifying the exact switch with open circuit fault will aid in replacement of one single switch instead of replacement of complete system and can reduce e-waste as well. In this paper we use current variation between various phases and the rotor angle, with the healthy state value to identify the fault in less than 1/8th cycle of the current.

Field oriented control (FOC) of induction motor (IM) powered by a three-level voltage source inverter (3L -VSI) with space vector (SV) based continuous and dis -continuous pulse width modulation (PWM) is presented in this paper. The current error variations in each sector with above-mentioned PWM techniques are monitored and analyzed mathematically. These boundary investigations play a great role in the implementation of Current Error Space Phasor (CESP) based hysteresis current controller (HCC) which incorporates the advantages of a constant switching frequency PWM fed three-level inverter (3LI) into highly dynamic current controlled – voltage source inverter. As a preliminary step, FOC of IM with the conventional space vector PWM and bus clamping PWM (BC30 and BC60) fed 3LI have been simulated using SIMULINK toolbox of MATLAB. Transient analysis of the drive with acceleration, deceleration, and load change studies with different switching schemes are analyzed with d SPACE RTI1103 experimentation on a 2.2 kW three-phase IM drive in detail.

AC motor drives fed from current-controlled power electronic converters are popular on account of their superior steady-state and transient performance. Hysteresis control is a popular current control technique, which needs modifications to compensate for its demerits. Appraisal of current error as a space phasor for implementing the hysteresis controller is one such modification. Current error space phasor (CESP)-based hysteresis controller for voltage source inverters-fed motor drives are capable of achieving superior dynamic performance. With the modified hysteresis current controller, the drive operates at a constant switching frequency and ensures an optimal switching vector selection. This article presents the analysis of CESP for a space vector-modulated indirect matrix converter (IMC). The modified algorithm for space vector modulation of IMC accommodates for the variations in dc-link voltage since CESP is input voltage dependent. The boundary for the hysteresis current controller is calculated from the computed values of CESP. The time-varying nature of the hysteresis boundary ensures a constant switching frequency operation for IMC. Thus, a CESP-based hysteresis controller is proposed for the vector control of the IMC-fed permanent magnet synchronous machine (PMSM) drive. Experimental results are presented for validating the performance of the proposed controller.

This paper introduces a micro compensator which is installed and maintained by an electric utility for improved power quality in low voltage secondary distribution systems. Envisaged as a shunt-connected current-controlled voltage source inverter at 400 V level, a micro compensator performs reactive and harmonic compensation during peak periods. Thereby the power factor and the power quality at the point of common coupling are improved. During off-peak periods, a micro compensator provides dynamic reactive current support to compensate for voltage sag or voltage swell. The weighing factors which regulates the contribution of each compensation are quantitatively derived from voltage measurements at the point of common coupling. The proposed method to calculate reactive and harmonic compensation indices is validated in realistic systems. Frequency domain analysis shows that the harmonic compensation can be achieved in both static and dynamic modes. Analytical predictions based on frequency domain analysis are verified with experimental results which shows notable improvement in power quality levels.

A STATCOM that employs a nearly constant switching frequency hysteresis current controlled VSI is presented in this paper. Hysteresis controller enhances the dynamic performance of STATCOM. The switching frequency variations associated with the conventional hysteresis current controller is reduced by using a variable hysteresis boundary. Variable hysteresis boundary is predetermined by the current error, based on the sampled magnitudes of the reference voltage vector. This makes the switching frequency nearly constant and switching vector selection optimal. As a result, a voltage FFT profile similar to that of a space vector modulated STATCOM is obtained. Choosing a space vector based reference voltage vector keeps the current error within the pre‐calculated boundaries and improves the current tracking capability of STATCOM. The systematic method of selecting a switching sequence avoids random switching. Effectiveness of the proposed method for the control of grid‐connected STATCOM is experimentally verified and compared with a voltage‐controlled space vector modulated voltage source inverter based STATCOM. The hardware implementation of the controller for grid‐connected STATCOM is carried out in OPAL‐RT real‐time simulator platform and experimentally validated for a three‐phase balanced load of 5 kVA.