Current Sharing Control and Voltage Ripple Mitigation of a Dc Microgrid Supplying Constant Power Loads

CURRENT SHARING CONTROL AND VOLTAGE RIPPLE MITIGATION OF A DC MICROGRID SUPPLYING CONSTANT POWER LOADS

        Due to depleting reserves of conventional sources of energy, it has become inevitable to harness energy from non-conventional sources which are more eco-friendly and can be found in abundance in nature. Of these, India being a tropical country, solar energy plays a crucial role to meet the energy demand. It can be harnessed easily using Photo-Voltaic (PV) panels and can be easily stored in batteries for later use or to meet the peak load requirements. Presently, due to the presence of an infinite grid, it is inevitable to convert the dc voltage generated by the PV panels to ac voltage which may involve conversion in multiple levels. As some amount of power is wasted at each level of conversion, the overall efficiency of the system may fall under 70per-cent. Moreover, this power has to be again converted to dc as most of the loads used today, such as LED lighting systems, Television sets, PCs require dc power. This further reduces the overall efficiency of the system. To overcome these problems, one possible solution is use of a DC Microgrid with DG sources. A DC system has many advantages over an ac system, some of them are:

(a) Only active power needs to be controlled as reactive power component is absent in dc system,

(b) Skin effect and other losses are absent.

(c) Frequency control and harmonic problems are avoided.

        Also, considering high cost of renewable sources, high efficiency of the energy transfer from renewable sources to the load is demanded. Generation of electrical power near the point of consumption reduces transmission losses and hence improves the system efficiency. For the aforementioned reasons, micro-grids are identified as an effective method for power generation and distribution. DC micro-grids are gaining popularity due to high efficiency, high reliability, and easy interconnection of renewable sources as compared to the ac system. Decentralized generation utilizing distributed sources improves reliability over the centralized generation scheme.