For the selection of one concept from the two alternative generated SMGP concepts, the method of Pugh from Back, et al. (2008) can be utilized. Analyzing the strengths (advantages), weaknesses (disadvantages) and equivalence (equality) of the proposed concepts, it is possible to identify and choose the best concept to be adopted for the design of the product.
The three concepts alternatives are registered in Table 25 in the right columns, and on the left of the lines are placed the product/system requirements (specifications) and the weight of each requirement of the system that is extracted from the QFD and presented by the level of importance in percentage.
To indicate which of the concepts have positive points, negative or equivalence with each other, shall be used the following symbols:
(-1) drawbacks/disadvantage over the concept of reference; (0) equivalent to the concept of reference;
(1) advantage over the concept of reference.
In this method of Pugh presented in Table 25, the concept 1 will be used as the concept of reference.
Table 25: Pugh Matrix for selecting a concept.
Requirements of the product Value
(Weight) Concept 1 Concept 2 Concept 3
Dispatch and control the microgrid 9 0 0 0
High level monitoring of the microgrid in real-
time 7
0 0 -1
Optimal operation level by remote monitoring
over wire-less connection 7
0 0 0
High performance ability of the system 6 0 0 0
High level of automatic transition to/from and
operate islanded 6
0 0 1
High utilization of electric standards & protection
relays 6
0 0 0
High performance smart metering devices & bi-
directional converters 6
0 1 0
Optimal management of loads, demands and
outages of the microgrid 6
0 1 0
High control improvement with power
electronics 6
0 1 0
High level performance to detect, isolate and
restore faults in the microgrid 5
0 0 0
High energy storage and support capacity 5 0 1 0
High level stabilization of the AC-bus voltage
magnitude and frequency 5
0 0 0
Integration of a high level performing weather
station 4
0 0 0
Great enhanced interface infrastructure 4 0 0 0
High integration level of DER units in the
microgrid 4
0 0 0
Integrate a phasor measurement unit (PMU) 3 0 0 0
High level control for frequency, Volt/VAR in grid-
connected & island mode 3
0 0 0
High level integration of static switch and/or
source breakers 3
0 0 0
Total Sum (negative) 0 -7
Total sum (positive) 23 6
Source: Elaborated by the Author
From the results of the method of Pugh is concluded that the concept 2 is the best option according to the higher numbers of advantages available and this concept meets the requirements of the system the best. Even with this method of Pugh it is recommended to use common knowledge to decide which concept would be a better choice.
In concept 2, is the best alternative, because you have multiple inverters (power electronics devices) and the identified modules in the system can interface better with each other per individual block, which is not the case in concept 1. In concept 1, the main interface is the connection with the one and only hybrid inverter and if the microgrid has to be enlarged with extra DER systems, the complete system will have get out of operation and re- dimensioning of the complete SMGP would be required. Concept 3 also is a good option but considering all the requirements of the system in reference with concept 1, the concept 2 is the best alternative.
In Figure 37 is presented the location of the SMGP (Smart MicroGrid Platform) to be installed on the campus Gama. Not all the containers of the campus Gama are presented in this figure, since there were lastly are 13 containers set-up on the campus and the number is still growing. The location of the SMGP design will be in one of the containers, where the connection of the electrical energy distribution grid of the campus Gama is connected to the installed containers on the campus Gama in the one container containing a main breaker switch board. This will be further connected with the concept 2 of the SMGP as presented in Figure 35. The photovoltaic (PV) arrays will be installed on the roofs of the containers, including the main container with the installed SMGP that will function as a real-time laboratory environment. There are two lines from CEB to building UED and further to the container of the SMGP, because these are established by the distribution line connections to the SENTRON PAC 3100 multimeters in UED. All the connections to the container of the SMGP, such as the generator and PV arrays etc., will be further monitored and dispatched in the SMGP by the SCADA.Br software and additional data analysis tools and techniques.
Figure 37: The SMGP installation location on the campus Gama. Source: Elaborated by the Author
4.5 FINAL CONSIDERATIONS
After the completion of this conceptual design phase a concept model is given of the proposed SMGP system that will function as a real-time platform for laboratory studies, test and research. After the application of the heuristics, any ungrouped sub-functions should be assembled into an existing module or a new sub module that has interactions with other modules through their flows. This step ensures their assignment to a development team (Stone, 1997). Through the conceptual design phase, the tasks and functional structures of the system are presented with a modular approach methodology. This is done to validate a scientific schematic structure of the whole design of this SMGP system. At the end of this conceptual design phase, there were three concepts generated. To check which one could be more valid for further development has been utilized the Pugh method and common sense for these three concepts. Finally one concept is chosen, concept 2, for further development of the SMGP system. The flows as regarded to in this conceptual design are described as the interactions between the modules. This heuristic method uses flow information to identify the modules. As all methods to use, it is not possible to strictly apply methods to any system, as in this research, some modifications had to be done to apply tools and methods to have the outcome of modules for this SMGP system. As seen in the literature of product or system design methods a, the theory of design is not just an easy academic exercise, but a useful tool in real world applications.