Analysis of the Capacitor-Less D-STATCOM for Voltage Profile Improvement in Distribution Network With High PV Penetration

 ABSTRACT

Distributed Energy Resources (DERs) have disrupted the traditional electrical system. Grid connected photovoltaic (PV) systems deliver electric energy closer to the consumer, shifting the paradigm from centralized to distributed generation. The impact of the stochastic PV output power gives rise to potentially rapid voltage fluctuations. Reactive power compensation is needed to regulate the voltage profile to meet the relevant standards. Traditional approaches like switched capacitors cannot provide reactive power that is continuously adjustable at short time scales. This paper examines an alternative distribution static synchronous compensator (D-STATCOM) based on a matrix converter (MC) for the low voltage distribution networks with high PV penetration. This technology can extend service life by using inductors for energy storage. The converter being studied provides ancillary services, including reactive power support; the impact on reliability, operational constraints, and electrical behavior is demonstrated. The contribution of this paper is a detailed analysis and impact study of the capacitor-less D-STATCOM in high PV penetration distribution networks. The significance of this paper is that it studies the behavior of the power electronics converter and its interaction with the power systems without assuming or neglecting details of either. Compensation effects and reliability comparisons between the proposed capacitorless D-STATCOM and the incumbent

D-STATCOM technology are also studied in this paper.

INDEX TERMS

D-STATCOM, voltage profile, reactive power compensation, model predictive control, matrix converter, grid integration, renewable energy sources, high PV penetration, reliability of power electronics.

Block Diagram:

FIGURE 1. Line Drop Compensation Circuit.

Expected Simulation Results:

FIGURE 2. Results from QSTS simulation showing power flow and bus

                                                  voltage without D-STATCOM.

FIGURE 3. Results from QSTS simulation showing power flow and bus

                                                       voltage with D-STATCOM.

FIGURE 4. Impact of D-STATCOM on voltage profile of bus 890 without

                                                      and with high PV penetration.

CONCLUSION

This paper presented a detailed analysis and impact study of the capacitor-less D-STATCOM in high PV penetration distribution networks. This paper answered questions on (1) functional capabilities, (2) impact on the distribution network, (3) converter-level behavior, and (4) reliability of the proposed capacitorless D-STATCOM compared to other incumbent technologies (i.e., SVCs, VSC-based D-STATCOM, and OLTCs). The main contributions of this paper were:

 Impact study of capacitorless D-STATCOM on a distribution network with high PV permeability

 Impact and behavior comparison between capacitorless D-STATCOM and VSC-based D-STATCOM

 Reliability comparison between capacitorless D-STATCOM and VSC-based D-STATCOM

The significance of this paper is that it studies the behavior of the power electronics converter and its interaction with the power systems without assuming or neglecting details of either. In the power system study in this paper, a complete OpenDSS simulation of the IEEE 34 bus distribution test system was used to illustrate the impact of the capacitorless D-STATCOM during high PV penetration. In the power electronics study, the converter-level behavior of the capacitorless D-STATCOM was demonstrated with a 7.5 kVA experimental prototype. The main findings of this paper:

 The capacitorless D-STATCOM provides dynamic support to the distribution network allowing more PV penetration.

 The capacitorless D-STATCOM could precisely control the voltage and perform conservative voltage reduction to reduce losses, thus, improving the efficiency of the low voltage network.

 A distribution network with high PV penetration and a capacitorless D-STATCOM has shown fewer tap changes in mechanical OLTCs. Thus, increasing the service life of already existing distribution network equipment.

 A reliability study of the D-STATCOM technologies has shown that dc-link capacitors are the reliability bottleneck of the incumbent VSC-based D-STATCOM.

 The capacitorless D-STATCOM has the same compensation effects as the VSC-based D-STATCOM without relying on E-caps.

 A fault-tolerant capacitorless D-STATCOM has a 79% longer life than a fault-tolerant VSC-based DSTATCOM.

REFERENCES

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