1、英文原分Sequence analysis based DSP controller for Dynamic Voltage Restorer (DVR)Jayanti N. G., Malabika Basu*, Iurie Axente, Kevin Gaughan and Michael F. ConlonSchool of Electrical Engineering Systems Dublin Institute of TechnologyAbstractThe paper examines the behaviour of a Dynamic Voltage Restorer (
2、DVR) under balanced/unbalanced supply voltage sag condition, and restricted DVR injection capability (e.g. limited to 50% of the supply voltage injection). Sequence components of the supply voltage are extracted to generate the reference injected voltage for the DVR. The control determines the maxim
3、um possible positive sequence injection within the capacity of the compensator to achieve balanced voltage conditions at the load terminals. The control is verified through simulation and experimentation. The control algorithm has been implemented in a TI320F2812 fixed point DSP and the effectivenes
4、s of the controller is verified in a three-phase, 10kVA DVR laboratory prototype. In a three-phase, 240 V system, balanced sag and sag with magnitude and phase unbalance have been created, which is successfully compensated by the DVR with the proposed controller.I. INTRODUCTIONThe Dynamic voltage re
5、storer (DVR) offers sensitive voltage customers dynamic protection against system voltage disturbances originating from the incoming transmission/distribution system. DVRs could also form the series compensator part of Unified Power Quality Conditioners (UPQC) to serve the above purpose 1. Typically
6、 a DVR/UPQC is installed at the service entry point of sensitive voltage zone to compensate for voltage disturbances like sag/swell or unbalance, such that the voltage across a critical load terminal is perfectly regulated 3-6. In this paper a sequence based compensation strategy has been developed
7、to compensate balanced or unbalanced incoming voltage to regulate the load voltage. The advantage of the scheme is that under all conditions of unbalance, the DVR controller is able to compensate the unbalance, even if the voltage capability of the DVR is limited by its rating, which may be decided
8、by some other governing factors such as cost of the equipment, and/or over all UPQC rating.Fig. 1 shows the schematic diagram of a series compensated system for load voltage regulation. The DVR system consists of a three-phase voltage source converter (VSC), low pass filter and injection transformer
9、. The DVR is designed such that the maximum balanced voltage sag compensation is restricted to 50% of the supply voltage. The DVR is controlled from a TMS320F2812 TI fixed point DSP controller. The detailed parameters of the test system are described in Section III.Fig.1. Power circuit of DVRII. WOR
10、KING PRINCIPLE AND CONTROL OF DVRA. Working Principle of DVRA DVR maintains the load voltage at a predetermined level during any source voltage abnormal conditions such as voltage sag/swell or distortion. The working principle of the DVR can be explained with the help of Fig. 2. Three phase voltage
11、phasors Va1,Vb1 and Vc1 are balanced with 100% magnitude under normal operating condition. A fault in the upstream of the PCC can cause a balanced or unbalanced voltage disturbance at the PCC depending on the type of the fault.Fig.2. Voltage PhasorDuring an unbalanced fault situation, the phase volt
12、age vectors may be altered to Va2, Vb2 and Vc2. The situation here is that of a typical line to line fault which does not involve grounding. The DVR can inject appropriate voltages Vinja, Vinjb and Vinjc in order to build a balanced three phase system of voltage vectors Different types of voltage co
13、mpensation strategy are discussed 2-8. In 7 an attempt has been made to reduce the system losses by keeping the exchange of real power between the DC link and supply to a minimum. This is achieved by injecting voltages in quadrature to the supply current. This type of DVR does not need any DC link s
14、upport since no real power is involved in voltage injection. But during deeper sags, a high rating of inverter is necessary for compensatory action. The sequence component based analysis carried out in 8 suggests that the most economical voltage injection can be achieved by re-aligning the voltage v
15、ectors according to the positive sequence component.B. Sequence Component Control of DVRA sequence analysis based control strategy is adopted in this paper. The phase voltages are converted to balanced system of positive (V1), negative (V2), and zero(V0) sequence components. The DVR control aims to
16、maintain the positive sequence component at a predetermined value and to reduce the negative sequence and zero sequence components to zero. The zero sequence component in the three phase three wire system considered here is zero. Therefore, the injected voltage Vinj of a particular phase can be written as the vector sum of reference voltage (Vref), positive (V1) and negative(V2) sequence voltages, as given in (1). （1）
