Tint Soe Win

Constant DC capacitor voltage control based strategy for active load balancer in three-phase four-wire distribution system

Three-phase four-wire distribution systems are widely used in many countries. These power distribution systems are used for both three-phase three-wire loads and single-phase two-wire consumer appliances in South Korea, Myanmar and other countries. Unbalanced load conditions always occur in three-phase four-wire distribution systems. These unbalanced load conditions cause unbalanced voltages for three-phase and single-phase loads, and increase the loss in the distribution transformer. In this paper, we propose an active load balancer (ALB) based on constant DC capacitor voltage control for three-phase four-wire distribution systems. Constant DC capacitor voltage control is always used in active power line conditioners. The proposed control algorithm does not require any computation blocks to calculate the active and reactive currents on the distribution system. Balanced source currents with a unity power factor are obtained without any calculation blocks of the unbalanced active and reactive components on the load sides. The basic principle of the constant DC capacitor voltage control based strategy for the ALB is discussed in detail and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is also constructed and tested to validate the feasibility of the proposed control algorithm. Simulation and experimental results demonstrate that the proposed ALB can balance the source currents with a unity power factor for a three-phase four-wire distribution system.

Novel Simple Reactive Power Control Strategy With DC Capacitor Voltage Control for Active Load Balancer in Three-Phase Four-Wire Distribution Systems

This paper proposes a novel, simple reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy is applicable for adjustment of the source-side power factor under the balanced load condition. Only DC capacitor voltage control is used in the proposed control strategy. Therefore, the calculation blocks of the active and reactive components of the load currents are not necessary. The authors, thus, offer the simplest control strategy to control reactive power under the balanced load condition on three-phase four-wire distribution feeders. The basic principle of DC capacitor voltage control based reactive power control strategy is discussed in detail, and then confirmed by digital computer simulation. A prototype experimental system was constructed and tested. Experimental results demonstrate that balanced source currents with reactive power control are achieved on three-phase four-wire distribution feeders. These experimental results also demonstrate that controlling the reactive power reduces the required power rating of the ALB compared to that of the existing control strategy, which achieves balanced source currents with unity power factor.

A half-bridge inverter based Active Power Quality Compensator using a constant DC capacitor voltage control for electrified railways

This paper proposes a half-bridge inverter based Active Power Quality Compensator (APQC) using a constant DC capacitor voltage control for electrified railways. The APQC is composed of three-leg structured power devices with two common DC capacitors. Two legs perform as two half-bridge inverters, which compensate the unbalanced active, reactive and harmonic currents on the source side through DC capacitor. The third-leg controls two common DC capacitors voltages with a small amount of the output currents. Therefore the current rating of the third-leg devices can be reduced as compared to that of the already proposed three-leg structured APQC. For the control algorithm of the half-bridge inverter based APQC, a constant DC capacitor control based algorithm is used. Any calculation blocks of the unbalanced active, reactive and harmonic components of the load current are not needed. Thus we offer the simplest algorithm for the half-bridge inverter based APQC. The basic principle of the proposed half-bridge inverter based APQC using a constant DC capacitor voltage control is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that the proposed APQC can achieve balanced and sinusoidal source currents on the primary side of Scott transformer in the traction substations for electrified railways.

Reactive power control strategy based on DC capacitor voltage control for active load balancer in three-phase four-wire distribution systems

This paper proposes a reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy is based on constant DC capacitor voltage control, which is always used in active power line conditioners. Therefore, the proposed reactive power control strategy does not require active, reactive calculation blocks of load currents for the reference source current calculation. Balanced source currents with a predefined power factor can be achieved without unbalanced active and reactive components detection of the load currents. The basic principle of the reactive power control strategy for the ALB is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested to validate the feasibility of the proposed control algorithm. Simulation and experimental results demonstrate that balanced source currents with a predefined power factor are achieved in three-phase four-wire distribution systems.

A half-bridge inverter based Active Power Quality Compensator with a DC voltage balancer for electrified railways

This paper proposes a half-bridge inverter based Active Power Quality Compensator (APQC) with a DC voltage balancer for electrified railways. The APQC is composed of three-leg structured power devices with two common DC capacitors. The first two legs perform as two half-bridge inverters to generate compensation currents and the third-leg is used for DC voltage balancer. The first-leg is connected to α-phase and the second-leg is connected to β-phase. Two DC capacitors are connected in series and midpoint is grounded. These two half-bridge inverters exchange and balance active power for two feeders through two common DC capacitors and compensate reactive and harmonic components of the distorted load currents. The third-leg controls two common DC capacitors to balance voltage level of each other. Using proposed APQC, the primary side of Scott transformer attains balanced and sinusoidal source currents. The principle and control algorithm of proposed a half-bridge inverter based APQC is discussed in detail. The proposed APQC is confirmed by both the PSIM computer simulation software and prototype experiment system. Simulation results show that the proposed APQC can achieve balanced and sinusoidal source currents in secondary side of Scott transformer.

Active load balancer on three-phase four-wire distribution systems with constant DC capacitor voltage control for multiple loads

This paper deals with compensation performance of an active load balancer (ALB) with the constant DC capacitor voltage control based strategy under multiple feeders. Instantaneous power flow into the ALB show that the balanced source currents with a unity power factor are obtained on the feeder that is connected to the ALB. Thus the ALB is not over loaded although the constant DC capacitor voltage control based strategy is used under multiple loads. Digital computer simulation is implemented to confirm the validity and high practicability of the ALB with the constant DC capacitor voltage control based on strategy under multiple feeders. A prototype experimental model is also constructed and tested. Simulation and experimental results demonstrate that the ALB with the constant DC capacitor voltage control based strategy compensates the unbalanced active and reactive components on the ALB connected feeder while the unbalanced current conditions are remained on other feeders. Thus, the ALB is not overloaded even it is used in the multiple distribution feeders.