A review of grid-tied converter topologies used in photovoltaic systems

TLDR: In this article, a review of grid-tied architectures used in photovoltaic power systems, classified by the granularity level at which maximum power point tracking (MPPT) is applied, is presented.

Abstract: This study provides review of grid-tied architectures used in photovoltaic power systems, classified by the granularity level at which maximum power point tracking (MPPT) is applied. Grid-tied PV power systems can be divided into two main groups, namely centralized MPPT (CMPPT) and distributed MPPT (DMPPT). The DMPPT systems are further classified according to the levels at which MPPT can be applied, i.e. string, module, submodule, and cell level. Typical topologies for each category are also introduced, explained and analyzed. The classification is intended to help readers understand the latest developments of grid-tied PV power systems and inform research directions.

Figures

Fig. 2. Centralized maximum power point trackers without galvanic isolation.

Fig. 15. Circuit diagram of switched-inductor type subIDPP architecture

Fig. 1. Centralized maximum power point trackers with galvanic isolation

Fig. 6. Typical schematic circuits of DC/AC grid side converters

Fig. 16. Circuit diagram of subIPDPP system employing flyback converter topology.

Fig. 7. Circuits of LCL filters for grid interconnecdtion

Frequently asked questions

Q1. What are the contributions mentioned in the paper "A review of grid-tied converter topologies used in photovoltaic systems" ?

This study provides review of grid-tied architectures used in photovoltaic power systems, classified by the granularity level at which maximum power point tracking ( MPPT ) is applied. The DMPPT systems are further classified according to the levels at which MPPT can be applied, i. e. string, module, submodule, and cell level. 

Q2. Why is the capacitance rating at the PV module terminal significant?

due to the effect of double line frequency ripples in the single-phase interconnection, the capacitance rating at the PV module terminal is significant, e.g. 8.8 mF in [56, 64]. 

Q3. Why is the term pseudo DC link used in the literature?

Since the DC link voltage is no longer regulated to a constant level, the term pseudo DC link is referred to in the literature, [56, 63]. 

Q4. What is the power that is common to each submodule?

The power that is common to each submodule is processed only through the centralized DC/AC converter while the subIDPPs process only the mismatch power. 

Q5. What is the way to integrate a PV system into a grid?

Module-Integrated-Series InvertersModule-integrated-series inverter (MISI) is another option to be integrated with PV modules andperform MPPT and DC/AC conversion. 

Q6. What is the advantage of using MIDPPs?

The system takes advantage of utilizing standard string configuration since the MIDPPs carry only the mismatch current, [76- 79]. 

Q7. What are the main types of DMPPT?

Three types of submodule based DMPPT solution are commonly presented, which include: (a) subMISC architecture; (b) subIDPP architecture; and (c) isolated-port subIDPP architecture. 

Q8. What is the advantage of applying DMPPT at the submodule level?

Applying DMPPT at the submodule level provides even finer conversion granularity to reduce mismatch in comparison with the module-level solution, [21]. 

Q9. What are the disadvantages of a series connected system?

The drawback of such implementation also lies in the inflexibility and single power failure, which are common in any series connected system. 

Q10. What is the cost of a DMPPT system?

Communication among all MIDPP is generally required to achieve MPPT at the module level, which adds significant cost to the system. 

Q11. Why is a damping resistor required in series with the capacitor?

Due to the self-resonant nature, a damping resistor is required in series with the capacitor to suppress oscillation, as shown in Fig. 7 (b). 

Q12. What is the topology of the module integrated parallel inverter?

The topology, shown in Fig. 6 (a), is capable of minimizing the overall capacitance since the constant DC link voltage is significantly higher than the PV module voltage. 

Q13. What is the main issue that prevents the integration of submodules?

One issue that prevents the straightforward integration of subMISCs is that submodules inside commercial PV panels are internally connected in series during the lamination process. 

Q14. How is the article accepted for publication in a future issue of this journal?

Two-stage and one stage conversion systems are shown in Figs.2 (a) and (b), respectively.(a)(b)This article has been accepted for publication in a future issue of this journal, but has not been fully edited. 

Q15. What is the name of the submodule-integrated-differential-power processor?

5.2. Submodule-Integrated-Differential-Power ProcessorsShown in Fig. 14 (b), an extension of MIDPP at the submodule-level is developed and known as asubmodule-integrated-differential-power-processor (subIDPP), [83]. 

Q16. What is the disadvantage of series connection of the MISI?

The series connection of the AC terminals is generally more challenging than the DC voltage stack since the requirement for control and coordination is higher.