Voltage regulation in renewable energy integration into the distribution network

Large-scale renewable energy (RE) integration into the distribution network (DN) causes uncertainties due to its intermittent nature and is a challenging task today. In general RE sources are mostly connected near the end user level, i.e., in the low voltage distribution network. RE integration introduces bi-directional power flows across distribution transformer (DT) and hence DN experiences with several potential problems that includes voltage fluctuations, reactive power compensation and poor power factor in the DN. This study identifies the potential effects causes due to large-scale integration of RE into the Berserker Street Feeder, Frenchville Substation under Rockhampton DN. From the model analyses, it has clearly evident that voltage of the Berserker Street Feeder fluctuates with the increased integration of RE and causes uncertainties in the feeder as well as the DN.

Highly linear low voltage low power CMOS LNA

A highly linear, low voltage, low power, low noise amplifier (LNA) using a novel nonlinearity cancellation technique is presented in this paper. Parallel Inductor (PI) matching is used to increase LNA gain by 3dB at the desired frequency. The linear LNA was designed and simulated in a TSMC 0.18μm CMOS process at 5GHz frequency. By employing the proposed technique, the IIP3 is improved by 12dB in contrast to the conventional folded cascode LNA, reaching −1dBm without having any significant effect on the other LNA parameters such as gain, NF and also power consumption. The proposed LNA also delivers a voltage gain (S21) of 12.25dB with a noise figure of 3.5dB, while consuming only 1.28mW of DC power with a low supply voltage of 0.6V.

Distinct disulfide isomers of μ-Conotoxins KIIIA and KIIIB block voltage-gated sodium channels

In the preparation of synthetic conotoxins containing multiple disulfide bonds, oxidative folding can produce numerous permutations of disulfide bond connectivities. Establishing the native disulfide connectivities thus presents a significant challenge when the venom-derived peptide is not available, as is increasingly the case when conotoxins are identified from cDNA sequences. Here, we investigate the disulfide connectivity of μ-conotoxin KIIIA, which was predicted originally to have a [C1–C9,C2–C15,C4–C16] disulfide pattern based on homology with closely related μ-conotoxins. The two major isomers of synthetic μ-KIIIA formed during oxidative folding were purified and their disulfide connectivities mapped by direct mass spectrometric collision-induced dissociation fragmentation of the disulfide-bonded polypeptides. Our results show that the major oxidative folding product adopts a [C1–C15,C2–C9,C4–C16] disulfide connectivity, while the minor product adopts a [C1–C16,C2–C9,C4–C15] connectivity. Both of these peptides were potent blockers of NaV1.2 (Kd values of 5 and 230 nM, respectively). The solution structure for μ-KIIIA based on nuclear magnetic resonance data was recalculated with the [C1–C15,C2–C9,C4–C16] disulfide pattern; its structure was very similar to the μ-KIIIA structure calculated with the incorrect [C1–C9,C2–C15,C4–C16] disulfide pattern, with an α-helix spanning residues 7–12. In addition, the major folding isomers of μ-KIIIB, an N-terminally extended isoform of μ-KIIIA identified from its cDNA sequence, were isolated. These folding products had the same disulfide connectivities as μ-KIIIA, and both blocked NaV1.2 (Kd values of 470 and 26 nM, respectively). Our results establish that the preferred disulfide pattern of synthetic μ-KIIIA and μ-KIIIB folded in vitro is 1–5/2–4/3–6 but that other disulfide isomers are also potent sodium channel blockers. These findings raise questions about the disulfide pattern(s) of μ-KIIIA in the venom of Conus kinoshitai; indeed, the presence of multiple disulfide isomers in the venom could provide a means of further expanding the snail’s repertoire of active peptides.

An effective VAR planning to improve dynamic voltage profile of distribution networks with distributed wind generation

This paper proposes an effective VAR planning based on reactive power margin for the enhancement of dynamic voltage stability in distribution networks with distributed wind generation. The analysis is carried over a distribution test system representative of the Kumamoto area in Japan. The detailed mathematical modeling of the system is also presented. Firstly, this paper provides simulation results showing the effects of composite load on voltage dynamics in the distribution network through an accurate time-domain analysis. Then, a cost-effective combination of shunt capacitor bank and distribution static synchronous compensator (D-STATCOM) is selected to ensure fast voltage recovery after a sudden disturbance. The analysis shows that the proposed approach can reduce the size of compensating devices, which in turn, reduces the cost. It also reduces power loss of the system.

Voltage profile improvement for distributed wind generation using D-STATCOM

This paper presents the application of FACTS devices for the enhancement of dynamic voltage stability in distribution networks with distributed wind generation. The analysis is carried over a test distribution system representative of the Kumamoto area in Japan. The detailed mathematical modelling of the system is also presented. Firstly, this paper provides simulation results showing the effects of higher and lower penetration of distributed wind generation on the voltage dynamics in a faulted system. Then, a distribution static synchronous compensator (D-STATCOM) is used to improve the voltage profile of the system. This analysis shows that D-STATCOM has significant performance to improve the voltage dynamics of distribution system compared to shunt capacitor.

Voltage stability analysis with optimum size and location based synchronous machine DG

Power loss of a distribution system can be reduced significantly by using optimum size and location of distributed generation (DG). Proper allocation of DG with appropriate size maximizes overall system efficiency. Moreover it improves the reliability and voltage profile of the distribution system. In this paper, IEEE 123 node test feeder has been considered to determine the optimum size and location of a synchronous machine based DG for loss reduction of the system. This paper also investigates the steady-state and dynamic voltage profile of that three phase unbalance distribution network in presence of DG with optimum size. This analysis shows that optimum size of DG at proper location minimizes the power loss as well as improves the dynamic voltage profile of the distribution system.

Voltage oscillations in power distribution networks in the presence of DFIGs and induction motor loads

This paper investigates the oscillatory behavior of power distribution systems in the presence of distributed generation. The analysis is carried out over a distribution test system with two doubly fed induction type wind generators and different types of induction motor loads. The system is linearized by the perturbation method. Eigenvalues are calculated to see the modal interaction within the system. The study indicates that interactions between closely placed converter controllers and induction motor loads significantly influence the damping of the oscillatory modes of the system. The critical modes have a frequency of oscillation between the electromechanical and subsynchronous oscillations of power systems. Time-domain simulations are carried out to verify the validity of the modal analysis and to provide a physical feel for the types of oscillations that occur in distribution systems. Finally, significant parameters of the system that affect the damping and frequency of the oscillation are identified.

Impact of high wind penetration on the voltage profile of distribution systems

In this paper, simulation results showing the effect of lower and higher penetration of distributed wind generation on the voltage profile in distribution systems have been presented. The analysis is carried out over two distribution test systems. The detailed mathematical modeling of the system is also presented. It also investigates the small-signal stability of distribution systems using eigenvalue approach. The analyses show that voltage variation problems occur in different nodes of the distribution networks with an increase of penetration level. However, proper selection of dispersion level can improve the voltage profile of the distribution systems