A high-voltage direct current (HVDC) generation system

Abstract

A high-voltage direct current (HVDC) generation system (100) comprises a prime mover (102), an AC generator (exciter) (104) with two separate windings producing sine and cosine wave AC voltages with a 90-degree phase shift, and two unidirectional voltage generators (UVG1 and UVG2) (106,108) mounted on a common shaft. The synchronization of UVG1 and UVG2 by the prime mover ensures the conversion of AC voltages into unidirectional voltages. The combination of these outputs, guided by the mathematical identity Sin2(θ) + Cos2(θ) = 1, results in a constant DC voltage output. This innovative approach eliminates the need for commutation techniques and offers scalability for generating DC voltages exceeding 500kV. The system to promotes synchronization, reduces waveform distortions, and includes ripple reduction mechanisms for enhanced DC voltage quality. Overall, the disclosed invention presents a comprehensive and streamlined solution for efficient HVDC generation.

Description

[0001] 1. TITLE OF THE INVENTION

[0002] “A HIGH-VOLTAGE DIRECT CURRENT (HVDC) GENERATION SYSTEM”

[0003] 2. APPLICANTS a) Name : VEERABHADRA ELITE

[0004] ELECTRODYNAMIC SOLUTIONS LLP b) Nationality : INDIAN c) Address : Plot No 149, Door No 202, Venkat Classic

[0005] Apartments, Road No 4, KTR colony, Nizampet, Medchai- Malkajgiri, Telangana- 500090

[0006] 3. PREAMBLE TO THE DESCRIPTION

[0007] COMPLETE

[0008] The following specification particularly describes the invention and the manner in which it is to be performed. 4. DESCRIPTION

[0009] Technical Field of the invention

[0010] The present invention generally relates to electrical engineering and power generation. More particularly, relates to the field of high-voltage direct current (HVDC) generation systems without commutation, where the efficient and cost-effective production of HVDC is critical for long-distance electricity distribution and interconnection between similar power plants.

[0011] Background of the invention

[0012] The generation and transmission of electrical power have been critical components of modern infrastructure. High-voltage direct current (HVDC) systems play a pivotal role in efficiently transmitting electricity over extended distances. Unlike traditional alternating current (AC) systems, HVDC systems have the advantage of lower line losses, reduced corona losses, and better controllability, making them particularly suitable for long-distance power transmission, grid interconnection, and renewable energy integration.

[0013] Historically, HVDC systems have relied on complex commutation techniques in which the direction of current flow is switched at regular intervals to maintain a unidirectional voltage. These commutation methods, often involving mechanical or electronic components, can introduce voltage ripples, require sophisticated control mechanisms, and increase the overall complexity and cost of the system. In addition, the dependence on power electronic devices, such as thyristors, MOSFETs, GTOs, SCRs, and TRIACs, can further escalate costs and introduce potential points of failure. Efforts to improve HVDC technology have been ongoing, with a focus on enhancing reliability, reducing conversion losses, and minimizing the environmental impact of power transmission. Advances in semiconductor technology and control systems have contributed to more efficient HVDC systems, but the challenges of commutation and the associated converter costs persist.

[0014] In the quest for more efficient and cost-effective HVDC generation, there is a growing demand for innovative solutions that eliminate the need for commutation, reduce dependency on costly power electronic components, and provide stable and ripple -free HVDC output. Such solutions have the potential to revolutionize the field of power transmission, making long-distance electricity transmission more economical, reliable, and sustainable.

[0015] The present invention addresses these challenges by introducing a novel system that directly generates HVDC without the need for commutation. By simplifying the generation process, this system offers a promising solution for cost-effective, reliable, and stable HVDC generation, with potential applications in power transmission, grid interconnection, and beyond.

[0016] Brief Summary of the invention

[0017] The following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key / critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

[0018] It is a primary object of the present invention to generate high-voltage direct current (HVDC) directly from DC generators without relying on commutation techniques to eliminates the complexities and maintenance associated with traditional commutationbased systems.

[0019] It is yet another object of invention to enhance the quality of the generated DC voltage using ripple reduction mechanisms to reduce minor / major ripples in the output.

[0020] It is yet another object of invention is designed to be scalable, allowing for cascading multiple instances to generate extremely high DC voltages including 500kV and above.

[0021] It is yet another object of invention is to eliminate the need for commutation techniques used in HVDC generation.

[0022] It is yet another object of invention is to facilitate the connection between two or more similar power plants with the same voltage, making it easier to integrate multiple power generation sources.

[0023] According to an aspect of the present invention, a system for the generation of high- voltage direct current (HVDC) that eliminates the need for commutation techniques is disclosed. The system comprises a prime mover, an AC generator (exciter), a first unidirectional voltage generator (UVG1), a second unidirectional voltage generator (UVG2), a common shaft.

[0024] In accordance with the aspect of the present invention, a system consists of various essential components:

[0025] Prime Mover: This component is responsible for providing rotational motion, which is essential for the system's operation. AC Generator (Exciter): The exciter contains two separate windings that generate AC voltages. One winding produces a sine wave, while the other generates a cosine wave has a 90-degree electrical phase shift relative to the sine wave.

[0026] Unidirectional Voltage Generators (UVG1 and UVG2): These two generators are mounted on a common shaft and are synchronized by the prime mover to maintain a consistent rotational speed.

[0027] Waveform Combination: The core principle of this system revolves around the mathematical combination of the square of the sine and cosine waveforms, as described by the equation Sin2(0) + Cos2(0) = 1. This combination results in a theoretically constant DC voltage output.

[0028] Synchronization: To ensure the generation of a constant and precise DC voltage, it is crucial that the prime mover, the AC generator (exciter), and the two UVGs rotate at the same speed. This synchronization is essential to prevent waveform distortions in the DC voltage output.

[0029] Unidirectional Voltage Generation: UVG1 and UVG2 play a crucial role in converting the AC voltages from the exciter's windings into unidirectional voltages to create the constant DC voltage.

[0030] Ripple Reduction: UVG1 may incorporate a compensating winding, which helps in reducing minor or major ripples in the generated DC voltage.

[0031] Insulation and Cascading: The common shaft is electrically isolated sections placed between two stages of unidirectional voltage generators to helps in limiting insulation levels. Furthermore, the system can be cascaded, allowing for the generation of DC voltages exceeding 500kV to permits grounding the negative voltage or connecting the center point of cascaded DC generators to the ground to manage insulation.

[0032] Elimination of Commutation: A significant advantage of this system is the elimination of commutation requirements, which are commonly associated with conventional HVDC systems using rectifiers and inverters. As a result, the system reduces reliance on power electronic devices, such as thyristors, MOSFETs, GTOs, SCRs, and TRIACs.

[0033] Further objects, features, and advantages of the invention will be readily apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings.

[0034] Brief Description of the Drawings

[0035] The invention will be further understood from the following detailed description of a preferred embodiment taken in conjunction with an appended drawing, in which:

[0036] Fig. 1 illustrates the block diagram of HVDC generation system, in accordance with an exemplary embodiment of the present invention.

[0037] Fig. 2 illustrates the general arrangement of conventional HVDC generation system, in accordance with an exemplary embodiment of the present invention.

[0038] Fig. 3a illustrates the diagram of SinO - sinusoidal emf generation in exciter winding - 1 from constant unit magnitude rotating magnetic field in the space, in accordance with an exemplary embodiment of the present invention. Fig. 3b illustrates the diagram of Cos0 - Cosinusoidal emf generation in exciter winding - 2 from constant unit magnitude rotating magnetic field in the space, in accordance with an exemplary embodiment of the present invention.

[0039] Fig. 4a illustrates the diagram of SinO - sinusoidal emf generation in exciter winding- 1 from constant unit magnitude rotating magnetic field in the space, in accordance with an exemplary embodiment of the present invention.

[0040] Fig. 4b illustrates the diagram of Sin20 - emf generation (uni-directional voltage) in UVG-1 from unit magnitude SinO rotating magnetic field in the space, in accordance with an exemplary embodiment of the present invention.

[0041] Fig. 5 a illustrates the diagram of CosO - Cosinusoidal emf generation in exciter winding- 2 from constant unit magnitude rotating magnetic field in the space, in accordance with an exemplary embodiment of the present invention.

[0042] Fig. 5b illustrates the diagram of Cos20 - emf generation (uni-directional voltage) in UVG-2 from unit magnitude cos 0 rotating magnetic field in the space, in accordance with an exemplary embodiment of the present invention.

[0043] Fig. 6 illustrates diagram of the Sin2(0) + Cos2(0) = 1 (constant DC voltage) emf generation in HVDC system, in accordance with an exemplary embodiment of the present invention.

[0044] Fig. 7a illustrates the diagram of salient pole stator type alternator / exciter for UVG-1 & UVG-2, in accordance with an exemplary embodiment of the present invention. Fig. 7b illustrates the diagram of cylindrical stator alternator / exciter for UVG-1 & UVG-2, in accordance with an exemplary embodiment of the present invention.

[0045] Fig. 8 illustrates the diagram of single-phase uni-directional voltage generators (UVG- 1 & UVG-2), in accordance with an exemplary embodiment of the present invention.

[0046] Fig. 9a illustrates the block diagram of n-stage HVDC generation system for more than 500kV, in accordance with an exemplary embodiment of the present invention.

[0047] Fig. 9b illustrates the block diagram of n-stage HVDC generation system individually connected, in accordance with an exemplary embodiment of the present invention.

[0048] Detailed Description of the invention

[0049] It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0050] The use of “including”, “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. Further, the use of terms “first”, “second”, and “third”, and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. According to an exemplary embodiment of the present invention, a system for the generation of high-voltage direct current (HVDC) that eliminates the need for commutation techniques is disclosed. The system comprises a prime mover, an AC generator (exciter), a first unidirectional voltage generator (UVG1), a second unidirectional voltage generator (UVG2), a common shaft.

[0051] In accordance with the exemplary embodiment of the present invention, wherein the prime mover serves as the mechanical source of rotational motion to ensures the system rotate at a consistent speed.

[0052] In accordance with the exemplary embodiment of the present invention, wherein the AC Generator (Exciter) comprises two separate windings, the first winding of the exciter is responsible for generating AC voltage in the form of a sine wave, while the second winding of the exciter generates AC voltage in the form of a cosine wave.

[0053] In accordance with the exemplary embodiment of the present invention, wherein the unidirectional voltage generators (UVG1 and UVG2) are mounted on a common shaft and are synchronized by the prime mover to maintain uniform and consistent rotational speeds, responsible for converting the AC voltage into unidirectional voltage.

[0054] In accordance with the exemplary embodiment of the present invention, is based on the mathematical formula Sin20 + Cos20 = 1 to describes the combination of a two-stage voltage generation process, in this process, one UVG generates voltage in the form of the square of a sine wave, and the other UVG generates voltage in the form of the square of a cosine wave. Combining these two waveforms theoretically results in a constant voltage waveform to producing a steady DC voltage output.

[0055] In accordance with the exemplary embodiment of the present invention, wherein the prime mover ensures that UVG1 and UVG2 rotate at the same speed, thereby maintaining faithful and proper DC voltage generation. Any deviation in the rotational speeds of UVGs and the exciter could lead to waveform distortions in the DC voltage output.

[0056] In accordance with the exemplary embodiment of the present invention, wherein the ripple reduction to address minor or major ripples in the DC voltage output, potential adjustments can be made during the design or development stages. These adjustments may include altering the number of turns in the UVGs or introducing compensating windings to reduce ripples caused by variations in the magnetic properties of the UVGs.

[0057] In accordance with the exemplary embodiment of the present invention, wherein the cascading of multiple DC generators, enabling the construction of DC voltages exceeding 500kV to limit the insulation levels of the windings, negative voltages can be connected to the ground, or electrically isolated shafts can be introduced between different stages of DC generators.

[0058] In accordance with the exemplary embodiment of the present invention, wherein the negative voltage can be connected to ground or center point of the cascaded DC generators can be connected to ground in order to limit the insulation level of the windings of the Unidirectional generators.

[0059] In accordance with the exemplary embodiment of the present invention, to reduces the convertor costs and reduces the dependability of power electronic devices such as Thyristors, MOSFETs, GTOs, SCRs, TRIACs etc., there is no commutation requirements.

[0060] Referring to Fig. 1, illustrates block diagram of the HVDC generation system (100) comprises a prime mover (102), a 2-phase AC generator (exciter) (104), a single phase first unidirectional voltage generator (UVG1) (106), a single phase second unidirectional voltage generator (UVG2) (108), a common shaft. The prime mover (102) creates a mechanical motion in the form of rotation. This mechanical energy powers an AC generator or exciter that has two distinct windings, one winding produces AC voltage in the form of a sine wave, and the other generates AC voltage in the form of a cosine wave. These windings are electrically phase-shifted by 90 degrees.

[0061] Two unidirectional voltage generators (UVG1 and UVG2) (106,108) are mounted on a common shaft and synchronized by the prime mover to ensure they rotate at the same speed. UVG1 takes the sine wave AC voltage from the exciter and transforms it into unidirectional positive voltage, while UVG2 does the same with the cosine wave AC voltage. Because both UVGs consistently produce positive voltages throughout the cycle and are synchronized, their outputs can be combined using the mathematical principal Sin2(0) + Cos2(0) = 1. This combination results in a constant and precise high- voltage direct current (HVDC) waveform, effectively eliminating the need for commutation techniques.

[0062] Fig. 2 illustrates the general arrangement of the HVDC generation system comprises a set of interconnected components designed to efficiently generate high-voltage direct current (HVDC). The yoke of the AC generator / exciter (1) provides structural support, magnetic path and housing electromagnetic poles (2) and associated electromagnetic pole coils (DC) (3) that generate the necessary magnetic fields. The exciter rotor windings -1 & 2 (AC) (4) on the shaft (5) produce AC voltages in the form of sine (Sin 0) and cosine (Cos 0) waves. These AC outputs are fed into the armature windings of the UVG 1&2, creating Sin20 and Cos20 outputs (10) for the system. The common shaft ensures synchronization of the components, including the single-phase unidirectional voltage generator windings (8) responsible for converting the AC inputs into unidirectional voltages. The yoke of UVG- 1 / 2 (9) bracing the unidirectional voltage generators windings, contributing to the overall stability of the system. The DC output of armature windings represents the final output (10), combining the unidirectional voltages to produce a theoretically constant DC voltage. This innovative arrangement eliminates the need for traditional commutation techniques and offers scalability for generating high DC voltages. The system's efficiency is further enhanced by proper synchronization, insulation control, and the strategic placement of components within the yokes.

[0063] Fig. 3a illustrates the diagram of SinO - sinusoidal emf generation in exciter winding- 1 from constant unit magnitude rotating magnetic field in the space, whenever a unit magnitude magnetic field is rotating in the space, the flux linkages with the uniformly distributed windings will be sinusoidal. Therefore, the induced electro -motive-force (e.m.f.) in the windings will be sinusoidal. The induced emf will be sinusoidal always with respect to windings depending on the position of the windings with respect to flux. The flux vector indicates the magnitude direction. The magnitude with respect to phase angle in the space is shown the above fig 3a. indicates the induced emf in the windings.

[0064] If exciter rotor winding- 1 are at the start point (0°) the total flux linkages with the windings are zero, results zero induced emf. As the rotor rotates in the space at 30° the flux linkages will be 50% of total maximum flux linkages with winding hence the magnitude of induced emf will be 0.5 per unit value of maximum induced emf. Similarly, at 45°, 60°, 90°, 120°.... 360° are 0.707, 0.866, 1.0, 0.866....,0 per unit respectively. Hence the generated induced emf is Sine wave (sinusoidal in nature) as in the case of ordinary alternators which was proven earlier in the academics.

[0065] Electro-motive-force (e.m.f.) will be proportional to Number of turns of the windings and rate of change of flux linking the windings.

[0066] E = N (dd» / dt) = d / dt

[0067] Where,

[0068] E = electro-motive-force (e.m.f.) in Volts N = Number of turns of the windings which are linked with flux

[0069] <h = Flux (in Weber) = N<h = Flux Linkages (Weber-Turns) dt = Change in time d<b / dt = Rate of change of flux (Weber / s) dY / dt = Rate of change of flux linkages (Weber-Turns / s).

[0070] Fig. 3b illustrates the diagram of CosO - Co-sinusoidal emf generation in exciter winding-2 from constant unit magnitude rotating magnetic field in the space, Similar to Sine wave, if a +90° electrically lead / shifted winding (winding-2) with respect to winding- 1 will produce Cosine wave form. Since the flux linkages will be maximum at the start point, hence maximum induced emf will be generated at 0° and zero induced emf at 90°.

[0071] Fig. 4a & 4b illustrates the diagram of SinO, Sin20 - emf generation (uni-directional voltage) in UVG-1 from unit magnitude sin 0 rotating magnetic field in the space, the magnitude of flux produced in the rotor is sine wave is shown in fig.4b and given below at various angles of rotation. During first half cycle (0-180°) the sine wave is positive hence positive flux produces, however, during the next half cycle (180° to 360° [0°]) it is in negative direction refer below table.

[0072] Since the rotor already rotates 180° during the second half cycle and the flux also reverses hence the resultant flux direction is positive with respect to stator windings as in the first half cycle. Therefore, during whole cycle of rotor the flux and induced emf is always positive irrespective of position of rotor. The magnitude of the induced emf is shown fig.4b, i.e., Sin20 wave form (uni-directional voltage) will be induced throughout of the cycle, hence induce emf will be positive always.

[0073] Fig. 5a & 5b illustrates the diagram of CosO, Cos20 - emf generation (uni-directional voltage) in UVG-2 from unit magnitude CosO rotating magnetic field in the space, the magnitude of flux produced in the rotor is Cos wave is shown in the below fig.5b and given below at various angles of rotation. During 270° (-90°) to 90° the Cosine wave is positive hence positive flux produces, however, during 90° to 270° it is in negative direction refer below table.

[0074] Since the rotor flux reverses between 90° to 270° hence the resultant flux direction is positive with respect to stator windings during 90° to 270° rotation of rotor. Therefore, during whole cycle of flux and induced emf is always positive irrespective of position of rotor. The magnitude of the induced emf is shown in the below fig.5b, i.e., Cos20 wave form (uni-directional voltage will be induced throughout of the cycle, hence induce emf will be positive always.

[0075] Fig. 6 illustrates diagram of the Sin20 + Cos20 =1 (constant DC voltage) emf generation in HVDC system, follows a two-stage generation process based on the mathematical identity Sin20 + Cos20 =1. In the first stage, Unidirectional Voltage Generator 1 (UVG1) (106) generates a voltage waveform that is consistently positive and unidirectional throughout its cycle, taking the form of the square of a sine wave. Simultaneously, Unidirectional Voltage Generator 2 (UVG2) (108) generates a voltage waveform in the shape of the square of a cosine wave, sharing the same positive and unidirectional characteristics. The innovation occurs in the second stage when the waveforms from UVG1 and UVG2 are combined. By adding the square of the sine wave to the square of the cosine wave, a constant value of 1 is obtained, resulting in a theoretically constant and accurate direct current (DC) voltage waveform. This ensures reliable HVDC generation without the need for commutation, offering minimal voltage ripple and stable performance.

[0076] Fig. 7a illustrates the diagram of salient pole stator type alternator / exciter for UVG-1 & UVG-2, is a multi-stage operation aimed at producing a stable and constant DC voltage output. The system initiates with the prime mover (102) providing rotational motion to the exciter rotor with separate windings 1 and 2 (4). These windings generate AC voltages in the form of sine (SinO) and cosine (CosO) waves. The SinO and CosO outputs (6) from the armature windings serve as inputs to the subsequent Unidirectional Voltage Generators (UVG-1 and UVG-2) (106,108) mounted on a common shaft (5) and synchronized by the prime mover (102). UVG-1 and UVG-2 convert the AC inputs into unidirectional voltages, maintaining synchronization to prevent waveform distortions. The mathematical combination of the outputs from UVG-1 and UVG-2, following the principal Sin20+ Cos20= 1, results in a theoretically constant DC voltage output. The salient pole design with distinct poles projecting outward contributes to the reliability and performance of the system, particularly in applications where slower speeds and consistent flux variation are desired.

[0077] Fig. 7b illustrates the diagram of cylindrical stator alternator / exciter for UVG-1 & UVG-2, functions through a systematic process initiated by the prime mover (102), which imparts rotational motion to the system. The yoke (1) provides structural support, and the electro-magnetic pole coil (3) generates a crucial DC field for excitation. The exciter rotor windings (4) labeled 1 and 2 produce AC voltages in the form of sine (SinO) and cosine (CosO) waves. These AC outputs (6) representing alternating current, are then directed to Unidirectional Voltage Generators (UVG-1 and UVG-2) mounted on a common shaft and synchronized by the prime mover, UVG-1 and UVG-2 convert the AC inputs into unidirectional voltages. The combination of these outputs, guided by the mathematical identity Sin20+ Cos20= 1, results in a theoretically constant DC voltage output. This cylindrical stator design, in conjunction with the identified components, ensures the stability and efficiency of the HVDC generation system, providing a reliable and scalable solution for high-voltage direct current generation.

[0078] Fig. 8 illustrates the diagram of single-phase uni-directional voltage generators (UVG- 1 & UVG-2), a common shaft ensures the synchronized rotation of both generators, denoted as UVG-1 (106) and UVG-2 (108). These generators, mounted on the common shaft, receive AC inputs (SinO & CosO) from the exciter armature windings via a synchronization mechanism driven by the prime mover. UVG-1 and UVG-2 play a pivotal role in converting the incoming AC voltages into unidirectional outputs. The synchronization ensures that both generators rotate at consistent speeds, preventing waveform distortions and contributing to the generation of a stable and constant DC voltage. Additionally, mechanisms for ripple reduction may be incorporated in UVG- 1 and UVG-2 to minimize minor or major ripples in the output, enhancing the quality of the generated DC voltage.

[0079] Fig. 9a illustrates the block diagram of n-stage HVDC generation system for more than 500kV, begins with a prime mover, such as an electric motor or another mechanical source, initiating rotational motion. This prime mover provides the essential mechanical energy to drive the entire system. The rotational motion is transferred to the AC generator or exciter, which features two separate windings. These windings produce AC voltages, typically in the form of sine and cosine waves, with a 90-degree electrical phase shift. The AC outputs from the exciter, represented as sine and cosine waves, are fed into multiple Unidirectional Voltage Generators (UVGs) mounted on a common shaft. The UVGs convert these AC inputs into unidirectional voltages. The mathematical combination of the square of the sine and cosine waveforms. This mathematical operation, adhering to the identity Sin2(0) + Cos2(0) = 1, results in a theoretically constant DC voltage outputs from multiple stages contributes to the final HVDC voltage.

[0080] Synchronization of the system to ensure that the prime mover, the AC generator (exciter), and the UVGs all rotate at the same speed, this prevents waveform distortions in the DC voltage output and ensures the stability of the system. Depending on the design, UVGs may incorporate ripple reduction mechanisms, such as compensating windings, to minimize minor or major ripples in the generated DC voltage. The common shaft may include electrically isolated sections between two stages of UVGs to limit insulation levels. The system is designed to be scalable, allowing for cascading multiple instances to generate DC voltages exceeding 500 kV. This cascading may involve connecting the negative voltage to the ground or the center point of cascaded DC generators to the ground to manage insulation.

[0081] The n-stage HVDC generation system combines mathematical principles, synchronization, and advanced components to achieve stable and scalable high-voltage direct current generation, exceeding 500 kV to elimination of commutation simplifies the system and enhances its reliability.

[0082] Fig. 9b illustrates the block diagram of n-stage HVDC generation system connected individually with n- prime movers to initiate the rotational motion.

Claims

5. CLAIMSI / We Claim:

1. A high-voltage direct current (HVDC) generation system (100), comprising: a prime mover (102), an AC generator (exciter) (104), a first unidirectional voltage generator (UVG1) (106), a second unidirectional voltage generator (UVG2) (108), a common shaft; a prime mover (102) configured for rotational motion; an AC generator (exciter) (104) equipped with two separate windings; the HVDC generation system (100) causes a first winding generating AC voltage in the form of a sine wave; the HVDC generation system (100) causes a second winding producing AC voltage in the form of a cosine wave with a 90-degree phase shift from the first winding; wherein, the first unidirectional voltage generator (UVG1) (106) and second unidirectional voltage generator (UVG2) (108) are mounted on a common shaft and synchronized by the prime mover to convert AC voltages into unidirectional voltages; and the said second unidirectional voltage generator (UVG2) (108) converts the AC voltage from the second (cosine wave) winding into unidirectional voltage to ensuring the production of a constant and accurate DC voltage output.

2. The system (100) as claimed in claim 1, wherein the combination of the square of sine wave and the square of cosine wave in the UVGs generates a theoretically constant DC voltage as defined by the mathematical formula Sin2(0) + Cos2(0) = 1.

3. The system (100) as claimed in claim 1, wherein the prime mover configured AC generator (exciter) (104) and the two UVGs (106,108) rotate at the same speed to prevent waveform distortions in the DC voltage output.

4. The system (100) as claimed in claim 1, wherein the first unidirectional voltage generator (UVG 1 and / or 2) (106,108) comprises a compensating winding to reduce minor / major ripples in the generated DC voltage.

5. The system (100) as claimed in claim 1, wherein the common shaft includes electrically isolated sections between two stages of unidirectional voltage generator to limit insulation levels.

6. The system (100) as claimed in claim 1 , further comprising a cascading mechanism for connecting multiple instances of the system, generating DC voltages of 500kV and above.

7. The system (100) as claimed in claim 1, wherein the second winding of the AC generator (exciter) has a phase shift of 90 degrees electrical relative to the first winding.

8. A method generating high-voltage direct current (HVDC) comprising the steps of: a. initiating a prime mover (102) to provide rotational motion; b. generating AC voltage in the form of a sine wave from the first winding of the AC generator (exciter); c. simultaneously generating AC voltage in the form of a cosine wave from the second winding of the AC generator (exciter) with a 90-degree electrical phase shift; d. synchronizing the two unidirectional voltage generators (UVG1 and UVG2) mounted on the common shaft to maintain uniform rotational consistent speeds; e. converting the AC voltage from the first (sine wave) winding into unidirectional voltage using the first unidirectional voltage generator (UVG1);f. converting the AC voltage from the second (cosine wave) winding into unidirectional voltage using the second unidirectional voltage generator (UVG2); g. combining the unidirectional voltage outputs of UVG1 and UVG2 to produce a constant and accurate DC voltage output.

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