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In this work, a multilevel 42-sided polygonal space vector structure for suppression of lower order harmonics for open-end induction motor (OEIM) drive applications is proposed. The proposed power circuit topology consists of two inverters feeding an OEIM from either side. The main inverter fed with a single dc-link providing active power for motoring operation is switched at low switching frequency. The secondary inverter fed with a capacitive supply is switched at high frequency to suppress lower order harmonics upto 39th order, up to the base speed of operation allowing maximum utilization of the dc-link. The advantages of lower order harmonic suppression in motor phase voltage, for polygonal space vector structures, are combined with multilevel inverter topology. This offers various advantages like multilevel operation with low inverter switching for the main power delivery inverter and harmonic suppression throughout the modulation range. The low switching frequency primary inverter generates harmonics of the order $6*k \pm 1$ , where $k = 1, 2, 3,{\ldots }$. The harmonics are suppressed by the capacitor-fed secondary inverter, which supplies only reactive power for suppression of lower order harmonics in motor phase voltage. Use of a single dc-link facilitates four-quadrant operation of the inverter. The proposed scheme is validated for steady-state and dynamic performance by experimental results. [ABSTRACT FROM AUTHOR]

An isolated multilevel bidirectional dc–dc converter is presented in this article to interface the low-voltage (LV) battery and the high-voltage (HV) propulsion inverter in electric vehicles. The proposed topology achieves a HV step-up ratio in the motoring mode by reconfiguring two split capacitor half-bridge circuits in series/parallel through the symmetrical modulation of a voltage bidirectional, two quadrant switch. This reconfiguration generates a high-frequency multilevel voltage output at the dc-bus side of the inverter, which reduces the output filter volume. The dc-bus voltage is regulated by the duty cycle modulation of the intermediary switch in the motoring mode, simplifying the sensing and control. During regenerative braking, the converter is operated with phase shift modulation between the HV half bridges and the LV full bridge to regulate the battery voltage. The presented modulation strategies achieve zero voltage switching for the full-bridge devices over a wide load range. A comprehensive analysis of the proposed multilevel converter in motoring and braking modes along with the design constraints and soft switching boundary conditions is presented in this article. Detailed experimental results on a 1.5-kW laboratory prototype are presented to verify the design approach and illustrate the converter performance. [ABSTRACT FROM AUTHOR]

DC-link-based variable speed constant frequency (VSCF) ac power generating system is being considered as one of the popular power architectures in the new generation aircraft to provide backup power to the 115 V, 400 Hz aircraft loads. These systems directly convert the variable frequency output of the generator to the fixed frequency of 400 Hz using a voltage source inverter. These inverters use dc-link capacitors that are heavy and space consuming. In aircraft, the weight requirement is very critical; hence, minimizing the dc-link capacitance is one of the major research challenges to achieve high power density in the VSCF power converter. In this article, novel control strategies to minimize the dc-link capacitance of the ac–dc–ac VSCF power converter are presented. The proposed control strategies enable to achieve 95% reduction in dc-link capacitance value when compared with the conventional control strategy, while the control is robust enough to meet MIL-STD-704F transient specification at the inverter output. The proposed strategies are validated through controller hardware-in-loop testing of the VSCF system based on an 80 kVA brushless synchronous generator and a four-leg inverter. The transient and steady-state operation of the VSCF system with a 95% reduction in dc-link capacitance has been verified for rated power operation. [ABSTRACT FROM AUTHOR]

The increasing penetration of renewable energy resources (RESs) leads to a continuous displacement of synchronous generators. Since the grid integration of RESs is usually achieved through inertialess power converters, the system inertia reduces and the power system frequency stability is compromised. Consequently, unexpected generator tripping, load shedding, and even blackouts may occur and pose a great threat to the system normal operation. In view of these challenges, this article explores the possibility of providing the inertia support from power-electronics interfaced smart loads. Specifically, a transformerless electric spring topology and the associated control strategy have been developed to provide a substantial inertia support from the noncritical load. As compared with existing inertia enhancement techniques, the proposed solution is cost-effective without the need of additional energy storage units. The smart load inertia provision capability is quantitatively analyzed and experimentally verified on a laboratory-scale test. In the testing results, 40% and 18% reductions of the rate of change of frequency and the maximum frequency deviation are, respectively, observed with a 12% smart load penetration ratio. [ABSTRACT FROM AUTHOR]

Due to current sensor errors, tolerance of power switching devices, and asymmetry of PWM gating driving pulses, grid-connected inverters without isolation transformer usually have certain amount of dc components injected to the ac grid. Many efforts, such as using a blocking capacitor, a current dc component feedback control, and a voltage dc component feedback control have been introduced to try to suppress the dc injection to the grid. This paper proposes a novel control strategy of suppressing dc current injection to the grid for a three-phase inverter by accurately sensing the dc component of line voltages of three-phase inverter and adding a dc component control loop. A dc suppression control scheme is presented, and the suppression performance of the proposed dc rejection method is evaluated and compared with the traditional method. Finally, the control scheme is verified on a 20-kW three-phase grid-connected inverter. [ABSTRACT FROM AUTHOR]

This paper proposes a novel harmonic suppression scheme for two-level inverter fed three-terminal induction motor drives using switched capacitive filter. Capacitor fed H-bridges used as filters are cascaded to conventional two-level inverter to eliminate fifth- and seventh-order harmonics for the full modulation range including a six-step operation. For the first time, two-level dodecagonal voltage space vector is implemented with single dc supply for three-terminal induction motor drive. Enabling the switched capacitive filtering at low-voltage domain and shifting the high frequency switching to the switched capacitive filter is shown. A uniform pulse width modulation technique is shown which charges and maintains the capacitor voltages while eliminating the fifth- and seventh-order harmonics for the full speed range. [ABSTRACT FROM AUTHOR]

This paper presents a nine-level inverter topology for an open-end induction motor drive requiring only eight switches per phase, using two three-level inverters with two isolated dc links in a 3:1 ratio. A space-vector-based formulation is used to determine pole voltages such that both inverters supply power to the load over the full modulation range, eliminating the possibility of dc bus overcharging. Proper selection of switching states ensures that all floating capacitor voltages are kept tightly balanced. A digital state machine is used to select sequences of switching states in order to eliminate deadtime-induced pole voltage transients, further improving the output-voltage quality. A level-shifted carrier-based pulse width modulation scheme is used. The steady-state and transient performance of this topology were verified and the experimental results are included. [ABSTRACT FROM AUTHOR]

Unbalance in a three-phase system is created due to single-phase loads and distributed single-phase renewable energy sources connected to the same system. This unbalance can be compensated locally at the point of common coupling using a three-phase four-wire grid-tied inverter. This paper presents a comparative study of three-phase four-wire inverter topologies to compensate for positive, negative, and zero sequence components of the current injected into the grid. The function of the inverter is to inject power to the grid and additional active power compensation (APC) to support unbalance, load reactive power, and load neutral current. Performance analysis and control of these topologies are being compared to evaluate utilization of dc link, size, control, and ease of implementation. A quantitative comparison of the topologies is provided to illustrate the advantages and disadvantages of the analyzed systems. The control algorithm has been presented to regulate the active and reactive power in each phase independently during both grid-connected and islanded modes. The analysis of three-phase 480-V 50-kV·A system based on three H-bridge converter is presented with simulation and experimental results. The experimental results validate the ability of the inverter to provide four-quadrant control of each phase independently. [ABSTRACT FROM AUTHOR]

This paper proposes a novel multiple-input bidirectional dc–dc power converter to interface more than two dc sources of different voltage levels. This finds applications in hybrid electric/fuel cell vehicles (FCVs), where different dc sources of unequal voltage levels need to be connected with bidirectional power flow capability. The converter can be used to operate in both the buck and boost modes with bidirectional power control. It is also possible to independently control power flow between any two sources when more than two sources are actively transferring power in either directions. The operation, analysis, and design of the converter are presented with different modes of power transfer. The proposed converter is demonstrated for FCV application using real-time hardware-in-the-loop system. Experimental results for a 5-kW system are presented, validating the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper proposes a vector control strategy for independent control of two permanent-magnet synchronous motors (PMSMs) using a single four-leg inverter (4LI). An expanded two-arm modulation to obtain a balanced three-phase output voltage is described. This paper also proposes a method to compensate for the fluctuations in the neutral point voltage of two split capacitors in the dc link. The experimental results show that independent speed and position control of two PMSMs can be achieved using a single 4LI with the proposed vector control method. [ABSTRACT FROM AUTHOR]

Efficient power conversion technologies are strategic to the advancement of fuel cell vehicles (FCVs). This paper presents an overview of power conditioning system (PCS) architectures for an FCV propulsion system. Two new power conversion topologies to obtain variable ac from the fuel cell system are proposed. The switching of the power devices are based on the proposed hybrid modulation technique that minimizes the switching losses in the inverter. The proposed converters do not use the dc-link filter capacitors. Elimination of the dc-link capacitor not only reduces the size and volume but also helps in retaining the sine wave modulated information at the input of a three-phase inverter. Bidirectional converter topologies are proposed for interfacing low-voltage battery and fuel cell dc bus. Experimental results are presented for the proposed topologies. [ABSTRACT FROM AUTHOR]

Extensive research done in the recent past has proven that power electronic converters and electric propulsion motors are extremely critical components for modem hybrid electric vehicle (HEV) propulsion applications. Therefore, it is essential that both the traction motor and the associated drive operate at their optimal efficiencies throughout the driving schedule. In typical HEV propulsion applications, the traction motor and the drive are used over the entire torque/speed operational range. In view of this fact, this paper aims at modeling the inverter and motor losses/efficiencies over typical city and highway driving schedules. The noteworthy losses within a typical three-phase dc/ac traction inverter, such as the switching and conduction losses for both the insulated-gate bipolar transistors and the antiparallel diodes, are modeled and simulated over the city and highway driving patterns. An induction motor (IM) is used for a medium-sized sport utility vehicle, which was modeled in the ADvanced VehIcle SimulatOR (ADVISOR) software. The significant IM losses that were considered in the study include the stator copper losses, rotor copper losses, and core losses. Thus, the average efficiencies of both the inverter drive and the induction traction motor are evaluated and summarized under city as well as highway driving conditions. Finally, based on the individual-model-based efficiency analysis, the overall traction motor drive system efficiency is estimated. [ABSTRACT FROM AUTHOR]