University of South Wales Master of Sciences Thesis
Standalone hybrid generation system for the remote area of Thar, Pakistan
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- 2.6.2. Power Electronics and Control Topology for Wind Generation
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Standalone hybrid generation system for the remote area of Thar, Pakistan practical issues are not shown in the diagram, such as the negative sequence regulation, d-q decoupling, etc. The inner central loop regulates current, and the other control loop regulates power. In some cases, the reactive power reference, Qref, could be a power factor reference. By controlling this reference, the injected current to the utility can be maintained at unity power factor. Also, a variation of the constant power control can be implemented to maintain the inverter DC bus voltage at a constant value. In that case, the active power Pref, can be replaced with Vdref, and Pout can be replaced with Vdout so the DC voltage is regulated to the set-point Vdref. The output of this outer control loop is the set point I*d, which is used as a reference signal to the current regulator. When DC bus voltage is increasing, meaning the power from the primary source is increasing; it is charging the DC capacitor. In order to maintain the DC bus voltage, the i*d will be increased so that the power can be transferred to the inverter output. 2.6.2. Power Electronics and Control Topology for Wind Generation A typical power electronics topology that is used for a permanent magnet synchronous generator is shown in Figure 16. The three-phase variable voltage, variable frequency output from the wind turbine is rectified using a diode bridge. With the change in the speed of the synchronous generator, the voltage on the DC side of the diode rectifier changes. To maintain a constant DC-link voltage of the inverter, a step-up chopper is used to adapt the rectifier voltage. As viewed from the DC inputs to the inverter, the generator/rectifier system is then modeled as an ideal current source. This rectified output signal from the diode bride is filtered into a smooth DC waveform using a large capacitor (Carrasco et al. 2006). The DC signal is then inverted through the use of semiconductor switches into a three-phase, 50 Hz waveform. This waveform can then be scaled using a transformer to voltage levels required by the utility’s AC system. The generator is decoupled from the grid by a voltage- sourced DC-link; therefore, this PE interface provides excellent controllable characteristics for the wind energy system. The power converter to the micro-grid enables a fast control of active and reactive power. However, the negative side is a more complex system where more sensitive power electronic parts are required. tải về 6.62 Mb. Chia sẻ với bạn bè của bạn:
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