Reactive Power Compensation Using Photovoltaic Inverter - Assignment Example

The system functions as both a reactive power compensator and an active power generator. These functions change with grid demands. Reactive power is supplied in large quantities at night than consumption.

At night current that is from the inverter to the grid is obtained from the DC capacitor. Power flow adjusted by the inverter is connected parallel to the main grid.
In order to inject some power into the grid, the DC capacitors' voltage value has to be greater than both inverters and the grids.
Active power injected depends on the phase difference between inverter output and the grid voltage.

Control
The controller compares reactive power injected with the reference reactive power hence resulting in an error power signal. The error is sent via PI controller and summed to the grid’s voltage in order in order to get a voltage amplitude equivalent to that of the inverter.
Active power generated by the inverter is compared with the reference active power signal to produce an error. Error passes via PI controller, giving rise to a loading angle. This loading angle is then summed to the grid’s voltage phase angle, hence resulting in an increased inverter phase angle.

Components
The Phase-Locked Loop will still recognize the fundamental positive sequence of the source voltage even in the worst cases scenarios of voltage harmonic distortion. At these conditions, the active filter absorbs balanced and sinusoidal currents from the source, which are in phase with a corresponding fundamental positive sequence of the source voltages.
The development of this regulation structure for active power filter is employed when combining with other structures that are to be connected in the dc-link bus. The structures are static converters that are capable of exchanging active power between an energy source or an energy storage device (capacitor at night). The inverter easily transfers this active power to the grid.

Energy Storage
A Power Conditioner with energy storage capability is a viable solution in improving the reliability and the qual¬ity of an electric energy supply. There are several tasks that are performed at a single time, for example, current harmonic reduction, smoothing of pulsating loads and reactive power com¬pensation. Moreover, the Power Conditioner should work as Uninterruptible Power Supply (UPS) at a short time during interruptions of the grid supply. The Power Compensator is flexible that is coupled to energy storage devices like supercapacitors and batteries.
The energy storage device (capacitor) is then connected to an inverter that allows DC-AC conversion.
The rectifier allows AC-DC conversion for the charging of the DC capacitor at night, the rectifier is in parallel with both the PV system and the DC capacitor.
At the inverter’s dc side, there is a capacitor that stabilizes the proper voltage level for better operation of the inverter that acts as a current source. The rectifier delivers dc power by charging capacitors, which can be used in normal operation time or at night.
By utilizing a portion of energy that is stored in the dc capacitor, the filter will be capable of compensating for the load current unbalance or in the smoothening of source voltage unbalance effects.
Compensations in reactive power and harmonic current are obtained by using solutions for the filtering algorithm. The algorithms generate reference currents that a filter has to inject; eventually filtering performance, i.e. as a harmonic compensator, is provided by the use of high precision and high-speed current regulators.
The MPPT algorithm does the real-time process¬ing of voltage and current ripple from PV system usually gener¬ated via switching operation from PWM in¬verter.
A phase-locked loop (PLL) is used to synchronize the converter and the system. PLL is extremely fast when compared to the inverter under normal grid operations, hence leads efficient tracking. At the transient condition of voltage depression or high system impedance, there is a limited delivery of active current at fast rates. There is a linear reduction in active current injection when terminal voltages are under 0.8 pu. At these transient states, the reactive current delivered maintains a high value, hence providing short circuit or voltage support strength.