This invention provides a Dual Hybrid Multilevel Converter (DHMC) (100). The DHMC (100) comprises a plurality of converters (102) configured to feed a grid in the DHMC (100). DC side chain-links (110) of each converter (102) of the plurality of converters (102) is inter-connected through one or more inter-connecting inductors (104). Each converter (102) of the plurality of converters (102) is associated with at least three phase-links (106) and single phase-link of each converter (102) comprises of an H-bridge (108) and one or more chain-links. The DHMC (100) further comprises at least three single phase transformers configured to receive output from each converter (102) for generating output voltage of the DHMC (100).
The DHMC contains two converters (converter-1 (102) and converter-2 (102)) wherein converter-1 and converter-2 are configured to exchange reactive power with the grid independently or parallelly, wherein the converter-1 and converter-2 are connected in a front to front fashion (coupled at their ac sides through the transformers) and also in a back to back fashion (the dc sides of converter-1 and converter-2 (parts-102) are also interconnected.
The proposed DHMC has the ability to operate in the full range of available modulation index without any additional third harmonic injection methods. During unbalanced grid conditions, the capacitor voltages of the proposed DHMC can be maintained at their reference value by injecting common mode voltage in the chain-links. Since, the same common mode voltage is injected in all the chain-links, it doesn’t appear in the grid. The capacitor voltages can also be controlled by regulating the circulating current flowing in the inter-connecting inductors. The energy storage requirement to generate an output of one MVA is 7.94 kJ, under balanced grid conditions, which is very less compared to existing multilevel configurations. The size of the capacitance, number of energy storing devices and number of switching devices required are also less compared to Delta Cascade H-bridge and Modular multilevel converters. The proposed converter contains switching devices that switch at fundamental frequency and operate in Zero Voltage Switching mode (ZVS) thereby reducing the switching loss.
The DHMC contains two converters (converter-1 (102) and converter-2 (102)) wherein converter-1 and converter-2 are configured to exchange reactive power with the grid independently or parallelly, wherein the converter-1 and converter-2 are connected in a front to front fashion (coupled at their ac sides through the transformers) and also in a back to back fashion (the dc sides of converter-1 and converter-2 (parts-102) are also interconnected.
The proposed DHMC has the ability to operate in the full range of available modulation index without any additional third harmonic injection methods. During unbalanced grid conditions, the capacitor voltages of the proposed DHMC can be maintained at their reference value by injecting common mode voltage in the chain-links. Since, the same common mode voltage is injected in all the chain-links, it doesn’t appear in the grid. The capacitor voltages can also be controlled by regulating the circulating current flowing in the inter-connecting inductors. The energy storage requirement to generate an output of one MVA is 7.94 kJ, under balanced grid conditions, which is very less compared to existing multilevel configurations. The size of the capacitance, number of energy storing devices and number of switching devices required are also less compared to Delta Cascade H-bridge and Modular multilevel converters. The proposed converter contains switching devices that switch at fundamental frequency and operate in Zero Voltage Switching mode (ZVS) thereby reducing the switching loss.
- Validated with simulations and theoretical analysis
- A prototype has been developed
- Experimental Results need to be analyzed to validate the operating principles
- Occupies less footprint and offers less cost and hence is likely to consume less funds from the government (save tax payers money) in the installment process.
- Improves power quality of the grid and hence prevents emergency loads (such as medical equipment, military equipment).
HITACHI Energy Private Limited, ABB, GENERAL ELECTRIC, SIEMENS, LARSEN & TOUBRO.
- Very much suitable for FACTS and high/medium voltage power system applications.
- Useful for high voltage and medium voltage applications, simple, easy to adopt, modular construction, energy storage required to generate an output of one MVA is less, lesser number of capacitors, lower capacitor size, lower switching losses, Zero Voltage Switching (ZVS soft switching) capability, can be applied to compensate unbalance in grid/load,
202021004129
518485