To meet several power objectives, the idea of organizing DGs into several clusters in a microgrid... more To meet several power objectives, the idea of organizing DGs into several clusters in a microgrid is proposed in this paper. Power objectives include maintaining active power flow to the main grid at a predetermined level, minimizing the reactive power flow to the main grid and maintaining a unified voltage profile across the microgrid. DGs are organized differently for active and reactive power control. All DGs realize active power objective in one group. As reactive power is used to maintain the unified voltage, DGs are grouped in several clusters to regulate multiple critical point voltages. The closest cluster to the point of common coupling, minimizes the reactive power flow and others manage their reactive power to regulate their critical points. Each cluster has a virtual leader which other DGs follow, utilizing the cooperative control. The cooperative law is also derived, based on the dynamics of the inverters. . is the Chief Technology Officer at Petra Solar where he leads the technology strategy and value proposition for Petra Solars unique sustainable and smart grid solution for power utilities. Johan has combined a 29 year career with leadership activities in industry and university in the USA, Europe and South Africa. He is a seasoned leader in transmission and distribution planning, wind and solar renewable integration, FACTS, HVDC, Distributed Power and Energy Storage. He is very experienced in R&D, planning, commercialization and integration of small and large-scale renewable wind and solar power plants in Africa, Europe and the USA. He was also the principal in establishing a new medium voltage, smart grid and power electronics research, development and testing laboratory in Arnhem, The Netherlands.
An improved full-bridge ZVS PWM using a twoinductor rectifier dddc converter is presented in this... more An improved full-bridge ZVS PWM using a twoinductor rectifier dddc converter is presented in this paper. For this improved topology, the main devices are switched on under zero-voltage (ZVS) conditions using the energy stored in the secondary filter inductors. In addition, it utilizes the low leakage inductance of a coaxial winding transformer to reset the currents in the rectifier diodes and eliminate the secondary voltage spike. The two-inductor rectifier has only one diode conduction drop in addition to frequency doubling in the output capacitor. The secondary filter size in the proposed topology is rather small. The advantages of the new topology include a wide loa d range with ZVS, no lost duty cycle due to diode recovery, no secondary voltage spikes, in addition to high power density and high efficiency.
Charge equalization for series connected battery strings has important ramifications on battery l... more Charge equalization for series connected battery strings has important ramifications on battery life. It enhances the uniformity of the battery cells and hence improves the life of the battery as a whole. A new charge equalization technique for a series string of battery ...
This paper deals with sensorless vector control of pulsewidth-modulated inverter-fed induction mo... more This paper deals with sensorless vector control of pulsewidth-modulated inverter-fed induction motor drives equipped with a three-phase diode rectifier. An electronically controlled braking resistor across the dc link is not used. Instead, the power regenerated during braking is dissipated in the motor while a dc-link overvoltage controller limits the braking torque. Losses in the motor are increased by an optimum flux-braking controller, maximizing either the stator voltage or the stator current depending on the speed. Below the rated speed, the braking times are comparable to those achieved using a braking resistor. The proposed braking scheme is very simple and causes no additional torque ripple. Experimental results obtained using a 2.2-kW induction motor drive show that the proposed scheme works well.
2014 IEEE 23rd International Symposium on Industrial Electronics (ISIE), 2014
ABSTRACT This paper proposes a new single-phase inverter topology for Photovoltaic (PV) applicati... more ABSTRACT This paper proposes a new single-phase inverter topology for Photovoltaic (PV) applications. The capability of decoupling the double-line-frequency ripple, using a small capacitance, is the main feature of the proposed topology. This allows for using a film capacitor instead of an electrolytic capacitor, resulting in higher inverter reliability. Additionally, no extra circuitry is needed to manage the transformer leakage energy.
To meet several power objectives, the idea of organizing DGs into several clusters in a microgrid... more To meet several power objectives, the idea of organizing DGs into several clusters in a microgrid is proposed in this paper. Power objectives include maintaining active power flow to the main grid at a predetermined level, minimizing the reactive power flow to the main grid and maintaining a unified voltage profile across the microgrid. DGs are organized differently for active and reactive power control. All DGs realize active power objective in one group. As reactive power is used to maintain the unified voltage, DGs are grouped in several clusters to regulate multiple critical point voltages. The closest cluster to the point of common coupling, minimizes the reactive power flow and others manage their reactive power to regulate their critical points. Each cluster has a virtual leader which other DGs follow, utilizing the cooperative control. The cooperative law is also derived, based on the dynamics of the inverters. . is the Chief Technology Officer at Petra Solar where he leads the technology strategy and value proposition for Petra Solars unique sustainable and smart grid solution for power utilities. Johan has combined a 29 year career with leadership activities in industry and university in the USA, Europe and South Africa. He is a seasoned leader in transmission and distribution planning, wind and solar renewable integration, FACTS, HVDC, Distributed Power and Energy Storage. He is very experienced in R&D, planning, commercialization and integration of small and large-scale renewable wind and solar power plants in Africa, Europe and the USA. He was also the principal in establishing a new medium voltage, smart grid and power electronics research, development and testing laboratory in Arnhem, The Netherlands.
An improved full-bridge ZVS PWM using a twoinductor rectifier dddc converter is presented in this... more An improved full-bridge ZVS PWM using a twoinductor rectifier dddc converter is presented in this paper. For this improved topology, the main devices are switched on under zero-voltage (ZVS) conditions using the energy stored in the secondary filter inductors. In addition, it utilizes the low leakage inductance of a coaxial winding transformer to reset the currents in the rectifier diodes and eliminate the secondary voltage spike. The two-inductor rectifier has only one diode conduction drop in addition to frequency doubling in the output capacitor. The secondary filter size in the proposed topology is rather small. The advantages of the new topology include a wide loa d range with ZVS, no lost duty cycle due to diode recovery, no secondary voltage spikes, in addition to high power density and high efficiency.
Charge equalization for series connected battery strings has important ramifications on battery l... more Charge equalization for series connected battery strings has important ramifications on battery life. It enhances the uniformity of the battery cells and hence improves the life of the battery as a whole. A new charge equalization technique for a series string of battery ...
This paper deals with sensorless vector control of pulsewidth-modulated inverter-fed induction mo... more This paper deals with sensorless vector control of pulsewidth-modulated inverter-fed induction motor drives equipped with a three-phase diode rectifier. An electronically controlled braking resistor across the dc link is not used. Instead, the power regenerated during braking is dissipated in the motor while a dc-link overvoltage controller limits the braking torque. Losses in the motor are increased by an optimum flux-braking controller, maximizing either the stator voltage or the stator current depending on the speed. Below the rated speed, the braking times are comparable to those achieved using a braking resistor. The proposed braking scheme is very simple and causes no additional torque ripple. Experimental results obtained using a 2.2-kW induction motor drive show that the proposed scheme works well.
2014 IEEE 23rd International Symposium on Industrial Electronics (ISIE), 2014
ABSTRACT This paper proposes a new single-phase inverter topology for Photovoltaic (PV) applicati... more ABSTRACT This paper proposes a new single-phase inverter topology for Photovoltaic (PV) applications. The capability of decoupling the double-line-frequency ripple, using a small capacitance, is the main feature of the proposed topology. This allows for using a film capacitor instead of an electrolytic capacitor, resulting in higher inverter reliability. Additionally, no extra circuitry is needed to manage the transformer leakage energy.
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Papers by Nasser Kutkut