Control of Multiport Converter to Integrate Solar PV and Energy Storage for Renewable Energy Applications

Abstract

DC-DC power converters have wide area of applications such as renewable energy, electric vehicle and smart grid system. Recently, great development is being made in power electronics dealing with renewable energy systems. Conventionally, in renewable energy systems, two port converters are used to connect the sources with the load and to integrate another source or an electric storage, a DC-DC converter is further used to provide the regulation that increases the losses and number of switches as well. However, multiport converter takes all the sources, battery and load connected to a single power conversion stage that is multiport power conversion stage, where all the sources and batteries are integrated via a port for renewable energy source and a bidirectional port for integration of a battery. In the proposed framework, a DC port provides three different voltage supplies of 24V,12V and 5V. A fourth AC port is provided for the AC loads whose voltage is controlled by a PI controller by using Clarke’s transformation. The three phase AC voltage is transformed into single phase using Clarke’s transformation so that a single PI controller can be used to control the AC voltage. Phase lock loop is used to extract the phase angle of the grid voltages in order to transform abc voltages to dq frame. The fourth AC port provides the flexibility of either, the system supplying power to the AC load or to the AC grid as well. When the power that is being produced by the panel is in surplus and the batteries are fully charged as well, the excess power will then be forwarded to the grid. Another advantage of the AC grid integrated with multi port converter is that we do not need extra power banks to store the charge when already a battery is fully charged, the battery can be discharged to supply power to the grid. A three level three phase inverter is used to convert DC into AC voltage. There are two loops that controls the inverter, the outer loop controls the Vdc and the inner loop controls the dq currents. The inner current controller generates the Vd and Vq signals which are then passed to the PWM generater to generate the gate pulse of the three phase inverter. The advantages includes an additional AC port, multiple DC voltage supplies and integration of grid with the multi port converter as well.