Changjiang Zhan

Dynamic voltage restorer based on voltage-space-vector PWM control

A dynamic voltage restorer (DVR) based on the voltage-space-vector pulsewidth-modulation algorithm is presented. Phase-jump compensation is achieved using a software phase-locked loop and a lead-acid battery energy store. A battery-charging control technique using the DVR itself is also described. To validate the control of the DVR, a three-phase prototype with a power rating of 10 kVA has been successfully developed. Simulation and experimental results are shown to validate the control methods.

Four-wire dynamic voltage restorer based on a three-dimensional voltage space vector PWM algorithm

A modified voltage space vector pulse-width modulated (PWM) algorithm for a four-wire dynamic voltage restorer (DVR) is described. The switching strategy based on a three-dimensional (3-D) /spl alpha//spl beta/O voltage space is applicable to the control of three-phase four-wire inverter systems such as the split-capacitor PWM inverter and the four-leg PWM inverter. In contrast to the conventional voltage space vector PWM method, it controls positive, negative and zero sequence components of the terminal voltages instantaneously. Three 3-D modulation schemes are analyzed with respect to total harmonic distortion (THD), weighted total harmonic distortion (WTHD), neutral line ripple and switching loss over the whole range of the modulation index when the DVR experiences both balanced and unbalanced sags with phase angle jumps. Experimental results from a 9 kW DVR system using a split-capacitor PWM inverter are presented to validate the simulation results.

Dynamic voltage restorer based on voltage space vector PWM control

A dynamic voltage restorer (DVR) based on the voltage space vector PWM (VSVPWM) algorithm is presented. Phase jump compensation is achieved using a software phase-locked loop (SPLL). A battery charging control technique using the DVR itself is also described. To validate the control of DVR, a three-phase prototype with a potential power rating of 10 kVA has been successfully developed. Simulation and experimental results are shown to validate the control methods.

Software phase-locked loop applied to dynamic voltage restorer (DVR)

In this paper, the analytical and practical design issues of a software phase-locked loop (SPLL) for DVR are presented. A SPLL model that uses a lag/lead loop controller, is derived in order to analyse the system performance and filtering characteristic by the use of bode diagrams and root-locus methods. In DVR applications, parameters of the design of the SPLL controller are not only dependent on the steady state and dynamic state, but also on practical conditions such as utility unbalance, voltage sag/swell magnitude, voltage harmonics, phase jumps and frequency variations. Therefore, the practical aspect of the SPLL implementation has also been discussed. Experimental results demonstrate its phase tracking capability.

Application of a Static Reactive Power Compensator (STATCOM) and a Dynamic Braking Resistor (DBR) for the Stability Enhancement of a Large Wind Farm

A control strategy to improve the stability of a large wind farm using a Static Reactive Power Compensator (STATCOM) and Dynamic Braking Resistor (DBR) is proposed and investigated. The STATCOM supplies the reactive power demand of the wind farm dynamically in order to maintain the network voltage. The DBR is controlled by Liapunovs stability criterion to absorb the active power of the wind farm during the network fault. The performance of the STATCOM and DBR, applied to a large wind farm (60MW), is studied in PSCAD/EMTDC. The simulation results show that effective control of the STATCOM and DBR together can enhance the stability of large wind farms.

Universal custom power conditioner (UCPC) with integrated control

This paper deals with the integrated control of a universal custom power conditioner (UCPC) applied to distribution systems. The proposed UCPC comprises a series PWM (pulse width modulation) converter and two shunt PWM converters with a battery energy storage unit for multi-function control. The goal of the UCPC is to utilize stored energy to achieve coordinated compensation functions such as short time uninterruptible power supply (UPS), voltage flicker control, dynamic voltage restorer (DVR), harmonic isolator or filter, power factor correction, system oscillation damping and interphase power controller using one device. It also manages a number of power quality and reliability problems simultaneously. The validity of the proposed UCPC with an integrated control method has been demonstrated through EMTDC/PSCAD simulation.

Novel voltage space vector PWM algorithm of 3-phase 4-wire power conditioner

This paper proposes a novel voltage space vector PWM algorithm that is applied to the control of voltage source inverters (VSI) when they operate as 3-phase 4-wire active power conditioners. The idea is based on the concept of 3-dimensional voltage space vectors (VSV) in an /spl alpha//spl beta/0 space. Under unbalanced conditions, the voltage switching state vectors are asymmetrical. A 3-dimensional voltage synthesis process can be carried out based on a normal VSV PWM method and splitting the zero vectors into different effective times, according to the 0 component. The new algorithm has been investigated thoroughly and can be implemented easily by the use of a digital-signal processor (DSP). The validity of the algorithm has been verified by the results of simulation. The proposed PWM strategy has the attractive feature that it can control 3 phases independently and flexibly in 4-wire systems.