Feel-soon Kang

A new single-phase five-level PWM inverter employing a deadbeat control scheme

A single-phase five-level PWM inverter is presented to alleviate harmonic components of the output voltage and the load current. Operational principles with switching functions are analyzed. To keep the output voltage sinusoidal and to have the high dynamic performances even in the cases of load variations and the partial magnetization in filter inductor, the deadbeat controller is designed and implemented on a prototype. The validity of the proposed inverter is verified through simulation and experiments. To assess the proposed inverter, it is compared with the conventional single-phase three-level PWM inverter under the conditions of identical supply DC voltage and switching frequency. In addition, it is compared with the five-level cascaded PWM inverter.

Multilevel PWM inverters suitable for the use of stand-alone photovoltaic power systems

This paper presents a new multilevel pulse width-modulation (PWM) inverter scheme for the use of stand-alone photovoltaic systems. It consists of a PWM inverter, an assembly of LEVEL inverters, generating staircase output voltages, and cascaded transformers. To produce high-quality output voltage waves, it synthesizes a large number of output voltage levels using cascaded transformers, which have a series-connected secondary. By a suitable selection of the secondary turn-ratio of the transformer, the amplitude of an output voltage appears at the rate of an integer to an input dc source. Operational principles and analysis are illustrated in depth. The validity of the proposed system is verified through computer-aided simulations and experimental results using prototypes generating output voltages of an 11 level and a 29 level, respectively, and their results are compared with conventional counterparts.

H-bridge based multilevel inverter using PWM switching function

This paper proposes an efficient PWM switching function for modified H-bridge based multilevel inverter. The prior H-bridge based multilevel inverter can increase the number of output voltage levels by adding switch components and dc input voltage sources. If it employs seven switches and three dc sources, the number of output voltage levels becomes seven. Although its THD characteristics are improved, it needs output filter to meet general output voltage THD requirement, i.e., 5 % below. To mitigate this problem, we propose an efficient PWM switching method for the prior H-bridge based multilevel inverter. By adding PWM switching schemes to the operation of the prior H-bridge switches, it can synthesize more sinusoidal waveform. By this simple alteration in the switching scheme, it can improve the output voltage THD requirement. To verify the high performance of the proposed switching scheme, we implemented computer-aided simulations and experiment using a prototype.

Multifunctional Onboard Battery Charger for Plug-in Electric Vehicles

This paper presents a multifunctional onboard battery charger for plug-in electric vehicles (PEVs). The proposed battery charger consists of three H-bridge modules including a selective switch, a high-frequency transformer, and inductors. The first duty of the proposed charger is to charge the propulsion battery when PEV connects to the ac grid [onboard charger (OBC)]. In this case, the proposed charger plays a role in ac-to-dc converting with power factor correction. Occasionally, the propulsion battery can supply surplus energy to the grid [vehicle to grid (V2G)]. In this second task, the proposed charger acts as an inverter. The third role is to charge the auxiliary battery via the propulsion battery when PEV is in a driving state [low-voltage dc-to-dc converter (LDC)]. In this case, the proposed charger acts as a step-down converter. In conventional PEVs, the aforementioned functions are done by an OBC and an LDC separately. The proposed charger can implement the three tasks by sharing switches and inductors in an all-in-one system. Thus, the proposed approach can realize a small and light design of the EV battery charger, resulting in the improvement of fuel efficiency. After theoretical analysis, we carry out simulations and experiments using a prototype to verify the validity of the proposed approach.

Seven-Level PWM Inverter Employing Series-Connected Capacitors Paralleled to a Single DC Voltage Source

This paper presents an effective circuit configuration of a multilevel inverter that can increase the number of output voltage levels with a reduced number of circuit components. The proposed seven-level pulsewidth-modulation inverter consists of a single dc voltage source with a series of capacitors, diodes, active switches for synthesizing output voltage levels, and an H-bridge cell. After theoretical analysis, we carry out computer-aided simulations and experiments to verify the validity of the proposed approach. Here, we also introduce a modified switching strategy to solve the capacitor voltage unbalancing that occurs in series-connected capacitors.

Series resonant sustain driver for AC plasma display

A new series resonant sustainer is presented to reduce the cost and power consumption of PDP TV, which employs address-and-display-period-separated (ADS) driving method. The proposed sustain driver can reduce the number of components compared with the prior approaches. It also improves the energy recovery efficiency about 3%. The operational principle and its features are illustrated and compared with the conventional approaches. The high-performance of the proposed sustain driver is verified by computer-aided simulations and experiments using a prototype equipped with a 7.5-inch diagonal panel, which is operated at 200 kHz switching frequency.

Hybrid Multilevel Inverter Connecting a Full-bridge Inverter to a 5-level Inverter in Series

This paper presents a circuit configuration of multilevel inverter to synthesize a large number of output voltage levels by connecting a full-bridge inverter to a 5-level inverter in series. We analyze the characteristics by computer-aided simulations and experiments when it has input voltage sources which have the same and the power of three in the amplitude. In addition, it is compared with the conventional transformer based multilevel inverter.

Multilevel Inverter using Two 5-level Inverters Connected in Series

This paper presents a circuit configuration of multilevel inverter to increase the number of output voltage levels by using conventional 5-level inverters connected in series. Most of all it can maximize the number of output voltage levels by employing input voltage sources, which have the power of five. When it synthesizes the same number of output voltage levels, the proposed inverter can save the number of switching devices compared with the conventional cascaded H-bridge cell inverter. So it can reduce the size, cost, power consumption of the system. We implemented computer-aided simulation and experiments for a 25-level inverter employing two 5-level inverters.

New approach for cascaded-transformers-based multilevel inverter with an efficient switching function

A new multilevel PWM inverter is presented to improve the system characteristic of a prior 11-level shaped PWM inverter scheme. In appearance, it consists of three full-bridge modules and three cascaded transformers; therefore, the configuration of the proposed multilevel PWM inverter is equal to that of the prior one. Only the turn-ratio of a transformer and its corresponding switching function are different from each other. Based on these differences, the proposed multilevel PWM inverter has two promising advantages. First, output voltage levels increase almost two fold. Consequently, it can generate more sinusoidal output voltage waves. Second, due to a suitable switching pattern, it lightens power imposed on the transformer, which is used for compensating output voltages with chopped pulses between steps. Operational principle of the proposed 19-level shaped PWM inverter is analysed with comparisons of the prior 11-level shaped PWM inverter. The validity of the proposed inverter system is verified by computer-aided simulations and experimental results based on a 1kW prototype.

Modification of cascaded H-bridge multilevel inverter to increase output voltage level with a single DC voltage source

It presents an effective circuit configuration of multilevel inverter which can increase the number of output voltage levels compared with the conventional cascaded H-bridge multilevel inverter. The proposed multilevel inverter consists of a dc input source with a series of capacitors, diodes, active switches for synthesizing output voltage levels, and an H-bridge cell. To generate seven levels in an output voltage, the proposed approach needs 7 switches. On the other hand, a traditional cascaded H-bridge multilevel inverter needs 12 switches. It can save five active switches resulted in cost saving with increasing the output voltage levels. Moreover, it is useful to extend output voltage levels by adding more active switches or the proposed module itself. To verify the validity of the proposed approach, we carry out computer-aided simulations and experiments. Here we also introduce a switching scheme to solve voltage unbalancing problem occurred in dc input voltage source with series-connected capacitors.