ABSTRACT:
With
the increase of dc based renewable energy generation and dc loads, the mediumvoltage dc (MVDC) distribution network is becoming a promising option for more
efficient system integration. In particular, large-capacity photovoltaic
(PV)-based power generation is growing rapidly, and a corresponding power
conversion system is critical to integrate these large PV systems into MVDC
power grid. Different from traditional ac grid-connected converters, the
converter system for dc grid interfaced PV system requires large-capacity dc
conversion over a wide range of ultra-high voltage step-up ratios. This is an
important issue, yet received limited research so far. In this paper, a
thorough study of dc-dc conversion system for a medium-voltage dc
grid-connected PV system is conducted. The required structural features for
such a conversion system are first discussed. Based on these features, the
conversion system is classified into four categories by series-parallel connection
scheme of power modules. Then two existing conversion system configurations as well
as a proposed solution are compared in terms of input/output performance, conversion
efficiency, modulation method, control complexity, power density, reliability,
and hardware cost. In-depth analysis is carried out to select the most suitable
conversion systems in various application scenarios.
KEYWORDS:
1. Photovoltaic generation
2. Dc-dc conversion
3. Medium voltage dc grid
4. Large-capacity
5. Ultra-high voltage transfer ratio
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig. 1 Topology of PDSR system solution
EXPECTED SIMULATION RESULTS:
Fig. 2 Cycle waves in steady state of the
solution of PDSR
Fig. 3 Power step response of the solution of
PDSR
Fig. 4 Cycle waves in steady state of the
solution of PDDS
Fig. 5 Power step
response of the solution of PDDS
Fig. 6 Cycle waves
in steady state of the solution of PPDS
Fig. 7 Power step
response of the solution of PPDS
CONCLUSION:
In this
paper, the emerging conversion systems for large-scale PV plants integrated
into MVDC grid are studied. The required structural features for such a conversion
system are discussed. The conversion system can be classified into four
categories by series-parallel connection scheme of power modules: PDSR, PPSR,
PDDS and PPDS. Features of each connection-scheme are qualitatively analyzed. A
solution of PDDS is also proposed in this paper. Through comparison of the
proposed solution with the existing solutions of PDSR and PPDS are conducted through
module topology analysis, simulation verification, and estimates of efficiency
and cost. The system-connection schemes PDDS and PPDS are most promising.
Usually, the PDDS scheme leads to high PWM frequency, good response, high power
density and high efficiency, but it has a high cost for active switches and has
common reliability. On the other hand, the PPDS scheme leads to low PWM
frequency, slow response, low power density, and common efficiency. But it has
a low cost of active switches and is highly reliable
REFERENCES:
[1]
A Q Huang, M L Crow, G T Heydt, et al. The future renewable electric energy
delivery and management (FREEDM) system: The energy internet. Proceedings of the
IEEE, 2011, 99(1): 133-148.
[2]
E Rodriguez-Diaz, J C Vasquez, J M Guerrero. Intelligent dc homes in future
sustainable energy systems: When efficiency and intelligence work together.
IEEE Consumer Electronics Magazine, 2016, 5(1): 74-80.
[3]
M Starke, L M Tolbert, B Ozpineci. AC vs. DC distribution: A Loss comparison. 2008
IEEE/PES Transmission and Distribution Conference and Exposition, 2008, Chicago,
IL, USA.
[4]
M Ding, Z Xu, W Wang, et al. A review on China’s large-scale PV integration:
Progress, challenges and recommendations. Renewable and Sustainable Energy Reviews,
2016, 53(9): 639-652.
[5]
F Li, C Li, K Sun, et al. Capacity configuration of hybrid CSP/PV plant for
economical application of solar energy. Chinese Journal of Electrical
Engineering, 2020, 6(2): 19-29.
