MV Substations Research Articles

Modular Multilevel Matrix Converter as Solid State Transformer for Medium and High Voltage AC Substations

The use of power converters as solid state transformers is an attractive solution to modernize the power network, but this solution has not been fully addressed for MV and HV substations. This paper presents a customized and simple control for the Modular Multilevel Matrix Converter (M3C), specially conceived for its operation on synchronous ports, which is the case of AC substations. The control allows bidirectional power transfer, generation/absorption of reactive power and provisions of ancillary services. The converter is compared to the back-to-back Modular Multilevel Converter (B2B-MMC) where the key performance indicators to carry out the comparison are power efficiency, number of semiconductor devices, passive components required, footprint, voltage cell balance, fault blocking capability and stress of components. The simulation results show the features, performance and attractiveness of the M3C topology in a 33/11 kV, 16 MW substation under different operating conditions, including grid faults and dynamic operation. The M3C presents similar efficiency and performance than the B2B-MMC, but it uses fewer semiconductor devices, passive components and total cell capacitor energy than the B2B-MMC, reducing cost and footprint. The experimental results show the performance of the M3C under less ideal conditions including a substation transformer saturation and power step response.

Power network-planning optimization considering average power not supplied reliability index: Modified by chance-constrained programming

In this paper, a mixed-integer linear formulation for optimization multi-stage power system is represented. In order to achieve the best results, all facilities should be considered simultaneously due to the interconnection between power network equipment. In this paper, power plant, HV and MV substations and Distributed Generation (DG) are regarded concurrently to create an integrated power system planning. Furthermore, a reliability index called Average Power Not Supplied (APNS) in load point is modelled. Stochastic programming in the Chance-Constrained approach is also utilized to overcome uncertain parameters containing demand in load points, nominal voltages and facility failure rates. The mathematical model is tested on a real life case study in four schemes containing with or without considering DG and in certain or uncertain environment. Using both DG and MV substation in schemes planning leads to the establishment of a parallel system to improve network reliability. Since each scheme has specific requirements, it’s mathematical formulation is discussed in detail. The proposed formulation determines the optimum system configuration, including feeder routing, siting and sizing for power plant, HV/MV substation and DG. The numerical results show that planning in uncertain environment has a higher cost in comparison with certain model, but the results are more close to real world operations. Based on the obtained results a planner can estimate the cost components in different environments. Also in uncertain schemes, the growth in confidence levels increases the grid total cost. Therefore, planners must create an appropriate balance between confidence level and system total cost. Numerical results suggest that using DGs leads to a decrease in the required substations, their power to service load points and APNS cost. Thus using DGs can be an economic alternative to decrease system total cost. The achieved results indicate that the proposed planning for designing a power network has a desirable performance in practice.

On Optimal Cost Planning of Low Voltage Direct Current Power Distribution Networks

In this article, optimal planning problem of large-scale urban power distribution network, in the presence of low-voltage direct current (LVDC) distribution technology, is formulated. The problem is modeled as a minimization of cost function comprising construction and loss costs. Simulations are performed on an urban test-case; spatial load forecasting is adopted and imperialist competitive algorithm (ICA) is utilized to find the optimal solution. Results show that the smaller sizes (large numbers) of MV substation (distribution transformer and rectifier) give the optimal solution. MV substations have standard sizes up to 2500 kVA; the proposed planning approach opted substations of size up to 315 kVA—for a total cost function comprising costs of LV feeders and MV substations.

Evaluation of lifetime of air-insulated switchgear versus service conditions in MV substations

Evaluation of lifetime of air-insulated switchgear versus service conditions in MV substations