AU2021100479A4 - Adaptive delta modulated modular multilevel converter - Google Patents

Adaptive delta modulated modular multilevel converter Download PDF

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AU2021100479A4
AU2021100479A4 AU2021100479A AU2021100479A AU2021100479A4 AU 2021100479 A4 AU2021100479 A4 AU 2021100479A4 AU 2021100479 A AU2021100479 A AU 2021100479A AU 2021100479 A AU2021100479 A AU 2021100479A AU 2021100479 A4 AU2021100479 A4 AU 2021100479A4
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signals
value
modulator
zero
array
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AU2021100479A
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Anshul Agarwal
Rahul Jaiswal
Richa Negi
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Agarwal Anshul Dr
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Agarwal Anshul Dr
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0012—Control circuits using digital or numerical techniques
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)

Abstract

A system of adaptive delta modulated modular multilevel converter, the converter comprising a switching modulator for generating an array of signals with a higher switch frequency, acomparator module for comparing each of the signals from the array and generating a high or a low status based on the value of the signals, thus generates discrete signals, a sample and hold circuit for capturing a device parameter of a continuously varying signal and holds the value for a predefined time interval, wherein a one-bit quantizer connected to the sample and hold circuit for analyzing the differences in an amplitude of the array of signals and an adaptive delta modulator for eliminating noise and adjusting slope of step size equal to slope of a modulating signal, thus obtaining a channel having an alternating sequence of zero-one. 29 a LLa 42. w L m ~ I

Description

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ADAPTIVE DELTA MODULATED MODULAR MULTILEVEL CONVERTER FIELDOFINVENTION
The present invention generally relates to a field of electrical engineering. More specifically, the invention relates to controlling a modular converter using a controller.
BACKGROUND OF THE INVENTION
Electrical converters, in particular in the medium and high voltage area, are used for converting a first current with a first frequency and a first voltage into a second current with a second frequency and a second voltage. Many types of converters are known such as for converting AC to AC, AC to DC, DC to AC and DC to DC.
Usually, converters comprise high power semiconductors for switching internally currents to produce the desired output current. In modular converters, these power semiconductors are distributed among converter modules, which also may comprise further components like a controller for the semiconductors or a capacitor for storing energy in the converter module.
A traditional two-level converter can be used in high-voltage, high power applications by series-parallel connection of matched power semiconductor devices. An application example is HVDC converters by ABB (called HVDC LIGHT). However, such converters have high dv/dt and di/dt,large EMI and common mode current, besides low efficiency.
The Modular Multilevel Converter (MMC) is one of the developing innovations these days. It has been attracted consideration for the researcher because of its favorable circumstances of particular outline, high effectiveness, and versatility, and superior output waveform with low losses. Due to the excellent configuration of MMC, there is a lot of research conducted based on the modeling and control technique of MMC and it is used for high and medium voltage applications.
Their characteristic measured quality takes into consideration an incalculable number of them to be associated in parallel and series arrangement to improve the current and voltage respectively, without any confounded interconnection prerequisites. The power circuit design takes into account excess task in instances of local faults in any of the modules. The control and modulation technique of MMC is very complex as compared to other converters.
In the vast majority of the acknowledge, all the state factors from the modules are detected and sent to a focal controller through optically disengaged committed Ethernet associations which makes all the control calculations and send the door signals to the switches in the different modules. While excess control frameworks can be utilized to guarantee that the framework isn't at risk to fall because of single point fault. That's why switching pulses play an important role in the controlling of the converters.
Researchers have introduced the idea of the Modular multilevel converter for clarifying the multilevel converter. The dc link capacitor of ordinary source inverters is used for the autonomous acknowledgment of the capacitor. In four quadrant operation, this type of converters doesn't require any other type of extra outer association with the sub modules. The switches are connected with the capacitance, the combinations of switches and dc storage capacitance are called sub module. If the number of sub module increases, the voltage level will increase and THD will also improve without increasing the difficulty level of the MMC.
However, the existing modulation techniques leads to more losses and the total harmonic distortion (THD) is poor.
In order to overcome the existing limitations, there is a need to develop a modulation technique that leads to reduced losses and improved performance in total harmonic distortion.
The technical advancements disclosed by the present invention overcomes the limitations and disadvantages of existing and convention systems and methods.
SUMMARY OF THE INVENTION
The present invention generally relates to a system and a method of improved modulation technique for modular multilevel converter.
An object of the present invention is to provide a convenient modulation technique with reduced losses.
Another object of the present invention is to increase the performance of total harmonic distortion .
Another object of the present invention is to design a converter for high and medium voltage applications.
According to an embodiment of the present disclosure a system of adaptive delta modulated modular multilevel converter comprises of a modulator, a converter, a detector, a focal controller, an ethernet. The modulator comprises of a comparator, a sample and hold circuit, an integrator and a one-bit quantizer.
The modulator is used for controlling the signals of the multilevel converter. The converter is a power electronic structure used for high voltage adjustable speed drives applications as well as power transmission applications and high-voltage direct current. The Modular Multilevel Converter (MMC) operates under favorable circumstances of particular outline, high effectiveness, and versatility, and superior output waveform with low losses. Due to the excellent configuration of MMC, it is used for high and medium voltage applications.Their characteristic measured quality takes into consideration an incalculable number of them to be associated in parallel and series arrangement to improve the current and voltage respectively, without any confounded interconnection prerequisites. The power circuit design takes into account excess task in instances of local faults in any of the modules. In the vast majority of the acknowledge, all the state factors from the modules are detected using the detector and sent to the focal controller through the optically disengaged committed Ethernet associations which makes all the control calculations and send the signals to a plurality of switches in different modules. The converters are controlled using switching pulses.
According to an embodiment, the switching pulses are fed to the switching modulator (SM) consists of a pair of IGBTs, at least two diodes, and the capacitor. The dc link capacitor of ordinary source inverters is used for the autonomous acknowledgment of the capacitor. The SM is ON when T1 is ON and T2 is OFF, while SM is OFF when T1 is OFF and T2 is ON. When the SM is ON, the SM voltage is the same as the SM capacitor voltage, while when it is OFF the voltage is zero. According to the SM state and the direction of the SM current, the current circulates through the capacitor producing its charge/discharge, or it does not circulate through the capacitor, maintaining its voltage.
The switches are connected with the capacitance, the combinations of switches and dc storage capacitance are called a sub module. If the number of sub module increases, the voltage level increases and THD also improves without increasing the difficulty level of the MMC.
The comparator circuit compares two voltages and outputs either a 1 or 0 to indicate which is larger. Comparators are often used, for example, to check whether an input has reached some predetermined value. The output of comparator must switch rapidly between the saturation level (+Vsat or -Vsat) and also respond instantly to any change of condition at its input.
According to an embodiment, the Sample and Hold Circuit, sometimes represented as S/H Circuit or S & H Circuit, is usually used with an Analog to Digital Converter to sample the input analog signal and hold the sampled signal. After this, the sampled value is hold until the arrival of next input signal to be sampled. The signals are sampled by continuously varying analog signal and holding its value at a constant level for a specified minimum period of time.
The integrator circuit outputs the integral of the input signal over a frequency range based on the circuit time constant and the bandwidth of the converter. The input signal is applied to the inverting input so the output is inverted relative to the polarity of the input signal. The integrator integrates the input voltage with respect to time. The output voltage is proportional to the input voltage integrated over time.
The 1-bit is known as a delta modulator (DM). In other words, DM codes the differences in the signal amplitude instead of the signal amplitude itself. The input signal is compared to the integrated output pulses and the delta (difference) signal is applied to the quantizer. The quantization level determines the number of grey levels in the digitized image after successful sampling. Since, the delta modulation transmits only one bit for one sample, therefore the signaling rate and transmission channel bandwidth is quite small for delta modulation.
According to an embodiment of the present disclosure,a flow diagram of a method of adaptive delta modulated modular multilevel converter.
Step 202 depicts generating an array of signals with a higher switch frequency using a switching modulator. The state factors of the modulator are detected and sent to the focal controller through optically disengaged ethernet association for control calculation. The control signals are sent to the switches in different modules for switching controls using different frequency.
Step 204 depicts comparing each of the signals from the array using a comparator module connected to the switching modulator and generating a high or a low status based on the value of the signals, wherein high is indicated as '1' for a greater value and low is indicated as '0'for a lower value, thus generates discrete signals.
Step 206 depicts capturing a device parameter of a continuously varying signal and holds the value for a predefined time interval using a sample and hold circuit connected to a comparator module, wherein a one-bit quantizer connected to the sample and hold circuit for analyzing the differences in an amplitude of the array of signals.
Step 208 depicts eliminating noise and adjusting slope of step size equal to slope of a modulating signal using an adaptive delta modulator, thus obtaining a channel having an alternating sequence of zero-one, wherein the signals are decoded and integrated to a zero value for generating a zero-one pattern with zero mean value.
According to an embodiment of the present disclosure, a block diagram for different modulation technique is categorized into various classes.The modulation technique is two types, afundamental switching frequency and a high switching frequency PWM. The switching frequency refers to the rate at which an electronic switch performs its function. The switching frequency is an important design and operating parameter in systems such as: A Class-D amplifier, an audio power amplifier with a switched-mode output. The fundamental switching frequency is denoted by (n = 1) is v = v/21.
The fundamental switching frequency is denoted by 'fo' and represents the initial value of the frequency preferably 0. The high switching frequency refers to the highest frequency. Further, the fundamental switching frequency is divided into 2 types: a space vector control and a selective harmonic elimination. The high switching frequency PWM is categorized into three parts: a space vector PWM, a selective harmonic elimination PWM and a sinusoidal PWM.
The space vector control modulation technique (SVM) is an algorithm for the control of modulation. It is used for the creation of alternating current (AC) waveforms; most commonly to drive 3 phase AC powered motors at varying speeds from DC using multiple class-D amplifiers. The selective harmonic elimination (SHE) method is used to reduce the quantity of Total Harmonic Distortion (THD) in a system.
According to an embodiment of the present disclosure, a schematic diagram for frequency dependent and frequency independent circuits for delta modulated modular multilevel converter. The Delta modulation and an adaptive delta modulation technique are one of the discontinuous type modulations techniques. The modulation technique is based on a switching frequency. The switching frequencies are classified into two parts, the first one is a lower switching frequency and another one is a higher switching frequency. The Delta modulation technique operates at lower switching frequency as well as higher switching frequency. Generally, delta modulation is preferred with higher switching frequency as the higher order harmonics is easily removed with the help of higher switching frequency. The discrete delta modulation has a high bandwidth, a high signal to noise ratio, a faster response, and a high resolution.
Delta modulation is a closed loop feedback system consisting of a comparator and a sample and hold in forward path and an integrator in a feedback path. There is two type of circuit, one is the frequency dependent and another one is a frequency independent.
According to an embodiment of the present disclosure, the frequency dependent circuit comprises of a comparator circuit that compares the input voltages entering the circuit and determines the greater value by assigning either a 0 or 1. The signal is sent to a sample and hold circuit. The circuit is an analog device that samples the voltage of a continuously varying analog signal and holds its value at a constant level for a specified minimum period of time. The comparator and the sample and hold circuits operates in a forward loop. The sampled signals are sent back to the input source through an integrator and a filter. The integrator performs the mathematical operation of integration with respect to time; that is, its output voltage is proportional to the input voltage integrated over time.
According to an embodiment of the present disclosure,the frequency independent circuit is similar to a dependent circuit except for the presence of the filter in the feedback loop of the frequency dependent circuit.
According to an embodiment of the present disclosure, an output pulse generated from delta modulation. The output pulse interprets an amplitude with reference to the time. The amplitude of the output pulses obtained from the delta modulator is discrete and represented in Y-axis. The sampled signals are held in the sample and hold circuit with respect to a particular time period and is denoted in X-axis.
According to an embodiment of the present disclosure,an adaptive delta modulated modular multilevel converter. The Adaptive delta modulator is same as a delta modulation except for an adaptive algorithm. The adaptive delta modulator has the capability to eliminate slope overload and granular noise.
Slope overload herein means a noise that generates when the slope of the input signal is greater than the delta modulator is capable of reproducing. The scenario arises when the S/N ratio is not too small, the noise power from these two sources is additive. It makes the slope of step size equal to the slope of the modulatingsignal.
The Step size should not be greater or smaller than the amplitude of the modulating signal. Hence the value of step size is an important parameter regarding the performance of delta modulation and converter. If the step size is too large, the signal willnot quantize properly and idle channel noise will appear. The pattern of the idle channel herein is an alternating sequence of zero-one specifying that the amplitude of the input signal is not varying. The signals obtained from the idle channel after decoding & integrate to zero and one gives the zero-one pattern which has zero mean value.
The sampled signals obtained from the sample and hold circuit is allowed to pass through a one-bit quantizer where the signals are quantized i.e. the differences in the signal amplitude is quantized instead of the signal amplitude itself. The input signal is compared to the integrated output pulses and the delta (difference) signal is applied to the quantizer. The continuous or the large set of values are converted to their discrete values. The quantized values are fed to the adaptive algorithm and undergoes mathematical calculations in order to improve the performance of the system.
According to the disclosure, the process of reconstructing the message signal at the receiver end from the sampled signals by using adaptive algorithm by converting the frequency domain signals in to their discrete time domain signals and removing the noise from the signals.
According to an embodiment of the present disclosure,an output pulse obtained from Modular multilevel converter with the help of delta modulation technique. The comparison of total harmonic distortion with different modulation techniques is depicted. The initial dc input voltage is 1200 volts and modulating index (m) is 0.9. The output voltage is obtained in the time domain, where the X-axis represents the time and the Y-axis represents the voltage. The output obtained from MMC with the help of delta modulation technique is sinusoidal voltage.
According to an embodiment of the present disclosure, an output Voltage THD of MMC with the help of delta modulation with arm inductance. The graph shows a relation between the frequency in X axis and the magnitude of Total harmonic distortion in Y-axis using an arm inductance for fundamental modulation. The term arm inductor used herein is used to limit the circulating current which flows within the converter. The total harmonic distortion of delta modulation is 13.15 % with arm inductance (L=0.25mH). The graph is plotted for the frequency of 50Hz having fundamental modulation of 517.5.
According to an embodiment of the present disclosure, an output Voltage THD of MMC with the help of delta modulation without arm inductance. The graph shows the frequency in Hertz in the X-axis and the magnitude of distortion in Y-axis. The frequency is considered to be 50 Hz, with fundamental modulation of 522.9. The total harmonic distortion of delta modulation is 4.9 %.
According to an embodiment of the present disclosure, an output Voltage THD of MMC with the help of adaptive delta modulation without arm inductance. The frequency is chosen to be 50Hz and the fundamental modulation is 520.5. The frequency is plotted in the X axis and the magnitude of distortion is in the Y-axis. The total harmonic distortion of adaptive delta modulation is 3 .8 2 % without arm inductance.
According to an embodiment of the present disclosure, comparisons of THD (in percentage) with different modulations technique without using arm inductor. The different values of different modulation techniques such as Pulse width modulation, delta modulation and adaptive delta modulation for increasing values of modulation index. The table shows that when the value of modulation index increases the value of pulse width modulation and delta modulation decreases. However, the value of adaptive delta modulation decreases halfway with the increasing value of modulation index, and then decreasing in the second half.
Based on the graphs and the tabular representation of the different modulation techniques with and without an arm inductor, it has been concluded that THD will improve when the delta modulation technique applies in place of other modulation technique. It has been observed that THD will also improve in case of without arm inductor. THD is 1 3 .15% with arm inductor but it is decreased to 4 .9 % without arm inductor.
The arm inductor plays a very important role. If arm inductor reduces or removes from the converter, the losses get reduced, that means THD improves. It has also been observed that the THD improves in case of adaptive delta modulation. In this case, the THD is 3 .8 2
% without arm inductor. Due to a lot of advantages of adaptive delta modulation as compared to delta modulation, the losses have been reduced. Further, the losses get reduced with the help of delta modulation and adaptive delta modulation techniques and the converter efficiency improves.
To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings
BRIEF DESCRIPTION OF FIGURES
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Figure 1 illustrates a block diagram of components installed in a system of adaptive delta modulated modular multilevel converter.
Figure 2 illustrates a flow diagram of a method of adaptive delta modulated modular multilevel converter.
Figure 3 illustrates a block diagram for different modulation technique.
Figure 4(A) and 4(B) illustrates a schematic diagram for frequency dependent and frequency independent circuits for delta modulated modular multilevel converter.
Figure 5 illustrates an output pulse generated from delta modulation.
Figure 6(A) and 6(B)illustrates a schematic diagram for adaptive delta modulated modular multilevel converter.
Figure 7 illustrates an output pulse obtained from Modular multilevel converter with the help of delta modulation technique.
Figure 8 illustrates a graphical representation of an output Voltage THD of MMC with the help of delta modulation with arm inductance.
Figure 9 illustrates a graphical representation of an output Voltage THD of MMC with the help of delta modulation without arm inductance.
Figure 10 illustrates a graphical representation of an output Voltage THD of MMC with the help of adaptive delta modulation without arm inductance.
Figure 11 illustrates a tabular view of comparisons of THD (in percentage) with different modulations technique without using arm inductor.
Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
DETAILED DESCRIPTION
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises...a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
Figure 1 illustrates a block diagram of components installed in a system of adaptive delta modulated modular multilevel converter 102. The system comprises of a modulator 110, a converter 102, a detector 104, a focal controller 106, an ethernet 108. The modulator 110 comprises of a comparator 112, a sample and hold circuit, an integrator 116 and a one-bit quantizer 118.
The modulator 110 is used for controlling the signals of the multilevel converter 102. The converter 102 is a power electronic structure used for high voltage adjustable speed drives applications as well as power transmission applications and high-voltage direct current. The Modular Multilevel Converter 102 (MMC) operates under favorable circumstances of particular outline, high effectiveness, and versatility, and superior output waveform with low losses. Due to the excellent configuration of MMC, it is used for high and medium voltage applications.Their characteristic measured quality takes into consideration an incalculable number of them to be associated in parallel and series arrangement to improve the current and voltage respectively, without any confounded interconnection prerequisites. The power circuit design takes into account excess task in instances of local faults in any of the modules. In the vast majority of the acknowledge, all the state factors from the modules are detected using the detector 104 and sent to the focal controller 106 through theoptically disengaged committed Ethernet 108 associations which makes all the control calculations and send the signals to a plurality of switches in different modules. The converters 102 are controlled using switching pulses.
The switching pulses are fed to the switching modulator 110(SM) consists of a pair of IGBTs,at least two diodes, and the capacitor. The dc link capacitor of ordinary source inverters is used for the autonomous acknowledgment of the capacitor. The SM is ON when T1 is ON and T2 is OFF, while SM is OFF when T1 is OFF and T2 is ON. When the SM is ON, the SM voltage is the same as the SM capacitor voltage, while when it is OFF the voltage is zero. According to the SM state and the direction of the SM current, the current circulates through the capacitor producing its charge/discharge, or it does not circulate through the capacitor, maintaining its voltage.
The switches are connected with the capacitance, the combinations of switches and dc storage capacitance are called a sub module. If the number of sub module increases, the voltage level increases and THD also improves without increasing the difficulty level of the MMC.
The comparator 112 circuit compares two voltages and outputs either a 1 or a 0 to indicate which is larger. Comparators 112 are often used, for example, to check whether an input has reached some pre determined value. The output of comparator 112 must switch rapidly between the saturation level (+Vsat or -Vsat) and also respond instantly to any change of condition at its input.
The Sample and Hold Circuit, sometimes represented as S/H Circuit or S & H Circuit, is usually used with an Analog to Digital Converter to sample the input analog signal and hold the sampled signal. After this, the sampled value is hold until the arrival of next input signal to be sampled. The signals are sampled by continuously varying analog signal and holding its value at a constant level for a specified minimum period of time.
The integrator circuit 116 outputs the integral of the input signal over a frequency range based on the circuit time constant and the bandwidth of the converter 102. The input signal is applied to the inverting input so the output is inverted relative to the polarity of the input signal. The integrator 116 integrates the input voltage with respect to time. The output voltage is proportional to the input voltage integrated over time.
The 1-bit is known as a delta modulator 110 (DM). In other words, DM codes the differences in the signal amplitude instead of the signal amplitude itself. The input signal is compared to the integrated output pulses and the delta (difference) signal is applied to the quantizer. The quantization level determines the number of grey levels in the digitized image after successful sampling.Since, the delta modulation transmits only one bit for one sample, therefore the signaling rate and transmission channel bandwidth is quite small for delta modulation.
Figure 2 illustrates a flow diagram of a method of adaptive delta modulated modular multilevel converter.
Step 202 depicts generating an array of signals with a higher switch frequency using a switching modulator 110. The state factors of the modulator 110 are detected and sent to the focal controller 106 through optically disengaged ethernet 108 association for control calculation. The control signals are sent to the switches in different modules for switching controls using different frequency.
Step 204 depicts comparing each of the signals from the array using a comparator module 112 connected to the switching modulator 110 and generating a high or a low status based on the value of the signals, wherein high is indicated as '1' for a greater value and low is indicated as '0' for a lower value, thus generates discrete signals.
Step 206 depicts capturing a device parameter of a continuously varying signal and holds the value for a predefined time interval using a sample and hold circuit 114 connected to a comparator module 112, wherein a one-bit quantizer connected to the sample and hold circuit 114 for analyzing the differences in an amplitude of the array of signals.
Step 208 depicts eliminating noise and adjusting slope of step size equal to slope of a modulating signal using an adaptive delta modulator 110, thus obtaining a channel having an alternating sequence of zero-one, wherein the signals are decoded and integrated to a zero value for generating a zero-one pattern with zero mean value.
Figure 3 illustrates a block diagram for different modulation technique. A modulation technique is categorized into various classes.The modulation technique is two types, afundamental switching frequency and a high switching frequency PWM. The switching frequency refers to the rate at which an electronic switch performs its function. The switching frequency is an important design and operating parameter in systems such as: A Class-D amplifier, an audio power amplifier with a switched-mode output. The fundamental switching frequency is denoted by (n = 1) is v = v/21.
The fundamental switching frequency is denoted by 'fo' and represents the initial value of the frequency preferably 0. The high switching frequency refers to the highest frequency. Further, the fundamental switching frequency is divided into 2 types: a space vector control and a selective harmonic elimination. The high switching frequency PWM is categorized into three parts: a space vector PWM, a selective harmonic elimination PWM and a sinusoidal PWM.
The space vector control modulation technique (SVM) is an algorithm for the control of modulation. It is used for the creation of alternating current (AC) waveforms; most commonly to drive 3 phase AC powered motors at varying speeds from DC using multiple class-D amplifiers. The selective harmonic elimination (SHE) method is used to reduce the quantity of Total Harmonic Distortion (THD) in a system.
Figure 4(A) and 4(B) illustrates a schematic diagram for frequency dependent and frequency independent circuits for delta modulated modular multilevel converter.
The Delta modulation and an adaptive delta modulation technique are one of the discontinuous type modulations techniques.
The modulation technique is based on a switching frequency. The switching frequencies are classified into two parts, the first one is a lower switching frequency and another one is a higher switching frequency. The Delta modulation technique operates at lower switching frequency as well as higher switching frequency. Generally, delta modulation is preferred with higher switching frequency as the higher order harmonics is easily removed with the help of higher switching frequency. The discrete delta modulation has a high bandwidth, a high signal to noise ratio, a faster response, and a high resolution.
Delta modulation is a closed loop feedback system consisting of a comparator 112 and a sample and hold in forward path and an integrator 116 in a feedback path. There is two type of circuit, one is the frequency dependent and another one is a frequency independent.
The frequency dependent circuit comprises of a comparator circuit 112 that compares the input voltages entering the circuit and determines the greater value by assigning either a 0 or 1. The signal is sent to a sample and hold circuit 114. The circuit is an analog device that samples the voltage of a continuously varying analog signal and holds its value at a constant level for a specified minimum period of time. The comparator 112 and the sample and hold circuits 114 operates in a forward loop. The sampled signals are sent back to the input source through an integrator 116 and a filter. The integrator 116 performs the mathematical operation of integration with respect to time; that is, its output voltage is proportional to the input voltage integrated over time.
Figure 4(B) represents the frequency independent circuit. The frequency independent circuit is similar to a dependent circuit except for the presence of the filter in the feedback loop of the frequency dependent circuit.
Figure 5 illustrates an output pulse generated from delta modulation. The output pulse interprets an amplitude with reference to the time. The amplitude of the output pulses obtained from the delta modulator 110 is discrete and represented in Y-axis. The sampled signals are held in the sample and hold circuit 114 with respect to a particular time period and is denoted in X-axis.
Figure 6(A) and 6(B) illustrates a schematic diagram for an adaptive delta modulated modular multilevel converter. The Adaptive delta modulator 110 is same as a delta modulation except for an adaptive algorithm. The adaptive delta modulator 110 has the capability to eliminate slope overload and granular noise.
Slope overload herein means a noise that generates when the slope of the input signal is greater than the delta modulator 110 is capable of reproducing. The scenario arises when the S/N ratio is not too small, the noise power from these two sources is additive. It makes the slope of step size equal to the slope of the modulating signal.
The Step size should not be greater or smaller than the amplitude of the modulating signal. Hence the value of step size is an important parameter regarding the performance of delta modulation and converter 102. If the step size is too large, the signal will not quantize properly and idle channel noise will appear. The pattern of the idle channel herein is an alternating sequence of zero-one specifying that the amplitude of the input signal is not varying. The signals obtained from the idle channel after decoding & integrate to zero and one gives the zero-one pattern which has zero mean value.
The sampled signals obtained from the sample and hold circuit 114 is allowed to pass through a one-bit quantizer where the signals are quantized i.e. the differences in the signal amplitude is quantized instead of the signal amplitude itself. The input signal is compared to the integrated output pulses and the delta (difference) signal is applied to the quantizer. The continuous or the large set of values are converted to their discrete values. The quantized values are fed to the adaptive algorithm and undergoes mathematical calculations in order to improve the performance of the system.
Figure 6(B) shows the process of reconstructing the message signal at the receiver end from the sampled signals by using adaptive algorithm by converting the frequency domain signals in to their discrete time domain signals and removing the noise from the signals.
Figure 7 illustrates an output pulse obtained from Modular multilevel converter 102 with the help of delta modulation technique. The comparison of total harmonic distortion with different modulation techniques is depicted. The initial dc input voltage is 1200 volts and modulating index (m) is 0.9. The output voltage is obtained in the time domain, where the X-axis represents the time and the Y-axis represents the voltage. The output obtained from MMC with the help of delta modulation technique is sinusoidal voltage.
Figure 8 illustrates an output Voltage THD of MMC with the help of delta modulation with arm inductance. The graph shows a relation between the frequency in X-axis and the magnitude of Total harmonic distortion in Y-axis using an arm inductance for fundamental modulation. The term arm inductor used herein is used to limit the circulating current which flows within the converter 102. The total harmonic distortion of delta modulation is 13.15 % with arm inductance (L=0.25mH). The graph is plotted for the frequency of Hz having fundamental modulation of 517.5.
Figure 9 illustrates an output Voltage THD of MMC with the help of delta modulation without arm inductance. The graph shows the frequency in Hertz in the X-axis and the magnitude of distortion in Y axis. The frequency is considered to be 50 Hz, with fundamental modulation of 522.9. The total harmonic distortion of delta modulation is 4.9 %.
Figure 10 illustrates an output Voltage THD of MMC with the help of adaptive delta modulation without arm inductance. The frequency is chosen to be 50Hz and the fundamental modulation is 520.5. The frequency is plotted in the X-axis and the magnitude of distortion is in the Y-axis. The total harmonic distortion of adaptive delta modulation is 3 .8 2 % without arm inductance.
Figure 11 illustrates a tabular view of comparisons of THD (in percentage) with different modulations technique without using arm inductor. The table shows different values of different modulation techniques such as Pulse width modulation, delta modulation and adaptive delta modulation for increasing values of modulation index. The table shows that when the value of modulation index increases the value of pulse width modulation and delta modulation decreases. However, the value of adaptive delta modulation decreases halfway with the increasing value of modulation index, and then decreasing in the second half.
Based on the graphs and the tabular representation of the different modulation techniques with and without an arm inductor, it has been concluded that THD will improve when the delta modulation technique applies in place of other modulation technique. It has been observed that THD will also improve in case of without arm inductor. THD is 1 3 .15% with arm inductor but it is decreased to 4 .9 % without arm inductor.
The arm inductor plays a very important role. If arm inductor reduces or removes from the converter 102, the losses get reduced, that means THD improves. It has also been observed that the THD improves in case of adaptive delta modulation. In this case, the THD is 3 .8 2 % without arm inductor. Due to a lot of advantages of adaptive delta modulation as compared to delta modulation, the losses have been reduced. Further, the losses get reduced with the help of delta modulation and adaptive delta modulation techniques and the converter 102 efficiency improves.
The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.
Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.

Claims (9)

WE CLAIM
1. A system of adaptive delta modulated modular multilevel converter, the converter comprising: a switching modulator for generating an array of signals with a higher switch frequency;
a comparator module connected to the switching modulator for comparing each of the signals from the array and generating a high or a low status based on the value of the signals, wherein high is indicated as '1' for a greater value and low is indicated as '0' for a lower value, thus generates discrete signals;
a sample and hold circuit connected to a comparator module for capturing a device parameter of a continuously varying signal and holds the value for a predefined time interval, wherein a one-bit quantizer connected to the sample and hold circuit for analyzing the differences in an amplitude of the array of signals; and
an adaptive delta modulator connected to the quantizer for eliminating noise and adjusting slope of step size equal to slope of a modulating signal, thus obtaining a channel having an alternating sequence of zero-one, wherein the signals are decoded and integrated to a zero value for generating a zero one pattern with zero mean value.
2. The system as claimed in claim 1, wherein the step size should not be greater than or smaller than the amplitude of the modulating signal.
3. The system as claimed in claim 1, wherein the alternate sequence of zero and one specifies that the amplitude of the input signal is not varying.
4. The system as claimed in claim 1, wherein the output signal obtained from the converter is a sinusoidal wave.
5. The system as claimed in claim 1, wherein the modulator has an inductance whose value is assigned to 0.
5. The system as claimed in claim 1, wherein a varying modulation index is provided to the modulator for achieving a desired total harmonic distortion.
6. The system as claimed in claim 1, wherein a detector is connected to the converter for detecting a desired set of state factors and sent to a focal controller through optically disengaged committed ethernet association for control calculation.
7. The system as claimed in claim 1, wherein the control signals are sent to a plurality of switches in different modules for switching controls using different frequency.
8. The system as claimed in claim 1, wherein a value for total harmonic distortion obtained from the modulator is found to approximately 3 .8 2 % with a frequency value taken to be 50Hz.
9. A method of adaptive delta modulated modular multilevel converter, the method comprising, generating an array of signals with a higher switch frequency using a switching modulator; comparing each of the signals from the array using a comparator module connected to the switching modulator and generating a high or a low status based on the value of the signals, wherein high is indicated as '1' for a greater value and low is indicated as '0' for a lower value, thus generates discrete signals; capturing a device parameter of a continuously varying signal and holds the value for a predefined time interval using a sample and hold circuit connected to a comparator module, wherein a one-bit quantizer connected to the sample and hold circuit for analyzing the differences in an amplitude of the array of signals; and eliminating noise and adjusting slope of step size equal to slope of a modulating signal using an adaptive delta modulator, thus obtaining a channel having an alternating sequence of zero-one, wherein the signals are decoded and integrated to a zero value for generating a zero-one pattern with zero mean value.
106 112 118 102 ONE-BIT COMPARATOR CONVERTER FOCAL QUANTIZER CONTROLLER 114 SAMPLE & 104 108 HOLD CIRCUIT DETECTOR ETHERNET 110 116 SWITCHING INTEGRATOR MODULATOR
FIGURE. 1
generating an array of signals with a higher switch frequency using a switching modulator
202
comparing each of the signals from the array using a comparator module connected to the switching modulator and generating a high or a low status based on the value of the signals, wherein high is indicated as ‘1’ for a greater value and low is indicated as ‘0’ for a lower value, thus generates 204 discrete signals
capturing a device parameter of a continuously varying signal and holds the value for a predefined time interval using a sample and hold circuit connected to a comparator module, wherein a one-bit quantizer connected to the sample and hold circuit for analyzing the differences in an amplitude of 206 the array of signals
eliminating noise and adjusting slope of step size equal to slope of a modulating signal using an adaptive delta modulator, thus obtaining a channel having an alternating sequence of zero-one, 208 wherein the signals are decoded and integrated to a zero value for generating a zero-one pattern with zero mean value
FIGURE. 2
FIGURE. 3
FIGURE. 4(A) FIGURE. 4(B)
FIGURE. 5
FIGURE. 6(A) FIGURE. 6(B)
FIGURE. 7
FIGURE. 8
FIGURE. 9
FIGURE. 10
FIGURE. 11
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