I appreciate your taking the time to give me your opinion and recommendation regarding a better way to go.
The results you linked only looked at 2x2 configurations with single bypass diodes per panel. There is zero reason to expect benefit from an extrapolated array with increased complexity.
How are you arriving at that that conclusion? If that conclusion is correct, then I can see my original question is not worth answering. However, that conclusion does not appear to be correct, because I'm finding TCT studies online which study larger arrays than 2x2, continuing to claim that TCT handles shade better than a standard xSyP configuration, and some TCT configurations which produce around 10% more power than other TCT configurations.
It seems to me that TCT has not been discussed much on these forums, so I'll summarize some of what I've found as I've tried to answer my question, in case it's helpful to others.
For example, from 2020, "An experimental study is also carried out using 16 number of 20 W solar panels connected in 4
×4 arrays and it is observed that the proposed method gives an enhanced power of
9.46%,10.70%,11.33%, and
18.06% as compared to TCT configuration for various shading patterns" (
https://www.tandfonline.com/doi/abs/10.1080/15567036.2020.1826008; another by some of the same authors at
https://www.proquest.com/openview/e...eaa176c920/1?pq-origsite=gscholar&cbl=2034442).
A similar article from 2021 at
https://ietresearch.onlinelibrary.wiley.com/doi/full/10.1049/iet-rpg.2020.0480 states a partial answer to my original question, "Because of numerous peaks, the MPPT can skip the right GMPP; this results in an additional power loss in the PV system, and a reduction technique is required to mitigate these losses. According to the literature, several authors have offered reconfiguration to the modules in the TCT PV array to distribute shading effects uniformly to achieve identical currents in each row to solve this problem." It concludes, "the proposed SA method enhanced the power generation of 9x9 TCT array by 26, 3.8, and 13% as compared to the TCT, GA, and SuDoKu methods under short-wide shading, respectively," "the proposed SA method enhanced the power generation of 9x9 TCT array by 13.2, 2.8, and 6.8% as compared to the TCT, GA, and SuDoKu methods under long-narrow shading, respectively," "the proposed SA method enhanced the power generation of 9x9 TCT array by 9.2, 1.9, and 7.6% as compared to the TCT, GA, and SuDoKu methods under short-narrow shading, respectively," and "the proposed SA method increased the power generation of 9x9 TCT array by 18, 2.8, and 15.2% as compared to the TCT, GA, and SuDoKu methods under centre shading, respectively." This results in a total income of $2538.20/year, compared to a standard TCT configuration's $1755.80/year, a $782.40 difference, using a partially-shaded 9x9 array of 170W panels. That $782.40 difference would probably pay for the extra connectors, wire, and perhaps fuses needed.
A 2016 study at
https://www.sciencedirect.com/science/article/abs/pii/S0038092X16301529 states "Study shows that changing the interconnection schemes of the modules from SP to TCT increases the power by more than 5% and the TCT configuration is considered as the best solution to lessen the mismatch losses under partially shaded conditions. An analysis based on probability theory indicates that introduction of cross ties (TCT or BL schemes) in the array almost doubles the life time of the array (Kaushika and Gautam, 2003). SP, TCT, BL, Simple Series (SS) and Honey Comb (HC) configurations have been compared in terms of maximum power and fill factor in Gautamand and Kaushika (2002). The TCT configuration has maximum power compared to other configurations under the same conditions of partial shading. The investigation shows that there is no additional cost for TCT-connected modules than SP-connected modules in large solar parks....One of the thrust areas of research recently in the field of partial shading is the implementation of modified classical MPPT techniques. When the bypass diodes conduct during non-uniform condition, P–V curve of the solar array shows multiple maxima. Thus the extraction of maximum power from the PV array becomes complex since there exist several local maximum power point (MPP) at low voltages and at higher voltages. Hence classical MPPT techniques which track the unique singular MPP in array characteristics under uniform irradiance conditions cannot be implemented. Under partial shading, the MPPT will identify a local optimal point as the global maximum point, thus leading to power losses. Approaches to track the global maximum power point (GMPP) have been demonstrated as in Wang and Hsu, 2011, Patel and Agarwal, 2008a, Patel and Agarwal, 2008b, Esram and Chapman, 2007, Safari and Mekhilef, 2011, but they tend to be complicated and many of them are unable to track the GMPP under changing illumination conditions. The development of different MPPT techniques to determine GMPP involving modified heuristic techniques is another recent area of research work." This answers part 1) of my question: no, the MPPT algorithm won't optimize the rounded steps well, unless they are smoothed out somehow.
A 2017 study at
https://www.sciencedirect.com/science/article/abs/pii/S0306261916316233 states regarding some algorithms that "the power output gains range from 19 to 140% compared to SP, and 13 to 68% compared to TCT."
A 2019 study at
https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/iet-rpg.2018.5675 concludes a "cost–benefit analysis of a 10 kWP grid-tied DPVA under different patterns of shade duration is presented. In comparison, the proposed M2 algorithm reports early payback period under high-intensity long-duration PSC. However, under low intensity and short duration shades, DPVA installation may not be necessary. Experimental tests of 4 × 2 size DPVA are conducted under different shade conditions. It is evident from experimental tests that the proposed algorithm has improved irradiance balance of shaded array from 40–47 to 92–97% and has improved output power by 37–104% compared to shade condition." In other words, in the cost-benefit analysis, TCT arrays were considered the baseline for such home-sized installations, and active algorithmic balancing (dynamic PV array or DPVA) has a shorter payback period (7 years) than TCT alone when there is more partial shading; when there is less partial shading the payback period was 15 years.
A 2019 article at
https://www.ije.ir/article_89987.html states "The maximum power increase is 26.5 percent of the total array output power."
A 2021 study at
https://www.techscience.com/iasc/v33n3/47095/html stated "Total Cross Tied (TCT) configuration is a commonly used now-a-days because it provides maximum power even under shaded condition," and showed the inverted triangle TCT algorithm produced a 7.8% power gain over other existing TCT configurations.
In 2022, an actively-switched TCT array produced 73.5% (of non-shaded power? or power gain? See figure 27) in partial shaded conditions, and made a nearly normal power curve which permitted the MPPT to optimize correctly: "During most shading conditions, the global peak with proposed reconfiguration appeared on the right side of the P-V curve eliminating the necessity of complex MPPT techniques. Thus the proposed system is simple and efficient." (
https://ieeexplore.ieee.org/document/9674916) That's a pretty good answer to my question.
So it would appear TCT research continues, and significant advancements are being made. The future of partially-shaded mobile solar power looks bright!
Furthermore, standard panels have 3 bypass diodes per panel making them perform superior to the simulated panels in a traditional 2S2P configuration.
IMHO, there's a reason these data are 10+ years old, and this has not become common practice.
There are numerous TCT studies with recent dates online, and note the comment above from 2021 about how it is "commonly used now-a-days."
