EP4035246A1 - Active power filter controlled by machine learning and method thereof - Google Patents
Active power filter controlled by machine learning and method thereofInfo
- Publication number
- EP4035246A1 EP4035246A1 EP20866990.3A EP20866990A EP4035246A1 EP 4035246 A1 EP4035246 A1 EP 4035246A1 EP 20866990 A EP20866990 A EP 20866990A EP 4035246 A1 EP4035246 A1 EP 4035246A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- current
- active power
- processing
- machine learning
- power filter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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Classifications
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B7/00—Heating by electric discharge
- H05B7/18—Heating by arc discharge
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06N—COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
- G06N20/00—Machine learning
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06N—COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
- G06N20/00—Machine learning
- G06N20/10—Machine learning using kernel methods, e.g. support vector machines [SVM]
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- 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
- H02J3/002—Flicker reduction, e.g. compensation of flicker introduced by non-linear load
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- 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
- H02J3/003—Load forecast, e.g. methods or systems for forecasting future load demand
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- 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
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- 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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/0003—Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
- H02P21/0014—Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control using neural networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/0003—Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
- H02P21/0025—Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control implementing a off line learning phase to determine and store useful data for on-line control
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/50—Vector control arrangements or methods not otherwise provided for in H02P21/00- H02P21/36
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06N—COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
- G06N3/00—Computing arrangements based on biological models
- G06N3/02—Neural networks
- G06N3/04—Architecture, e.g. interconnection topology
- G06N3/044—Recurrent networks, e.g. Hopfield networks
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06N—COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
- G06N3/00—Computing arrangements based on biological models
- G06N3/02—Neural networks
- G06N3/04—Architecture, e.g. interconnection topology
- G06N3/045—Combinations of networks
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06N—COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
- G06N3/00—Computing arrangements based on biological models
- G06N3/02—Neural networks
- G06N3/08—Learning methods
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- 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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00002—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by monitoring
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- 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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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- 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
- Y02E40/20—Active power filtering [APF]
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- 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
- Y02E40/70—Smart grids as climate change mitigation technology in the energy generation sector
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- 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
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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- 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
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/22—Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units
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- 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
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
- Y04S40/20—Information technology specific aspects, e.g. CAD, simulation, modelling, system security
Definitions
- the present invention relates to system, methods and arrangements for active power filters.
- Power electronic devices are applications, developed to control electricity energy flow in interaction with power supply systems. In a broad sense, all controllable power electronic devices are configured from solid-state circuits and control components circuit. It is common in industrial applications that power electronic devices are digitized to allow activities and interactions in power supply systems to be controlled by computing devices. As a result, large amounts of data is collected, enabling development of data driven methods, such as machine learning, as a next step. Methods for controlling and processing substantial amounts of signals in power electronic device is a relevant industrial and academic problem, currently being actively researched.
- a power supply system such as an electricity grid, comprises power generation, transmission and distribution subsystems, and Power Quality (PQ) is measured for each subsystem for long-term periods at certain sampling intervals. Therefore, especially for the problematic parts of the electricity grid, which are supplying highly nonlinear loads such as electric arc furnaces (EAF) or induction melting furnaces, huge amount of power quality event data is to be investigated, so that necessary countermeasures can be taken and compensation techniques can be developed specific to those parts.
- Power Quality filters and compensators are types of power electronic devices designed to compensate power quality events such as voltage dip, sag, interruptions and detect and filter out power quality variations such as harmonics and inter-harmonics.
- Machine learning typically refers to computational structures that can be programmed automatically by a learning algorithm.
- CN100461580 is disclosed a method for compensating by prediction of harmonic currents by measuring the loading current instantaneous value in real time and low passes the filtering, and gets the phase corner of the electric-net voltage by phase-locked loop at the same time; predicts the current volume of the sampling time currently according to the electricity-net current phase corner and the fitting parameter vector; adjusts the fitting parameter vector according to the predicted error; then, according to the adjusted fitting parameter vector, the electricity-net voltage phase corner and the requested compensatory controlling time- lapse, it can predict the loading current volume of the tk+DeltaT time; and predicts the request compensatory harmonic current signal of the tk+DeltaT at last.
- the disclosure provides a method for controlling and monitoring an active power filter, comprising the steps of: measuring current and previous states of current and voltage signals across at least a part of a power supply system and store these in a memory; pre-processing the current and volt age allowing for extraction and detection of features; predicting future current and volt age levels using a machine learning component; wherein the predicted future current and voltage levels are provided to a pulse width modulation controller in said active power filter device, allowing for a desired output to be obtained.
- a benefit of this method is that it allows for accurately predicting and compensating signal disturbances with the help of machine learning.
- the pre-processing may further comprise the steps of; extracting and detecting features by using a kernel-based method; processing said features using filters such as low-pass filter and exponential smoothing.
- the sample processing time and the harmonic error is kept at a minimum.
- the pre-processing may further comprise; performing a discrete Fourier Transform, fast fourier transform, recursive discrete fourier transform or any combination thereof.
- the extracted and detected features may be at least one of individual harmonics, inter harmonics, fundamental frequency, flicker, and/or any other disturbances such as power quality events or variations in the signals.
- the machine learning component may predict future voltage and current by predicting the amplitude and/or phases of at least one of fundamental component, harmonics, inter-harmonics at different frequencies as well as other power quality variations and events for at least one future cycle.
- a benefit of predicting amplitudes and/or phases for at least one future cycle is that it allows for the active power filter to compensate before any power quality events or variations occur.
- the machine learning component may comprise of a computational structure which is optimized using a learning algorithm, such as Artificial Neural Networks, Support Vector Machines, Decision Tree, Bayes Classifier or any combination thereof.
- a learning algorithm such as Artificial Neural Networks, Support Vector Machines, Decision Tree, Bayes Classifier or any combination thereof.
- the proposed methods allow for a more robust and accurate prediction of current and voltage levels.
- At least a part of said power supply system may supply electric arc furnaces.
- a benefit of applying the method on power supply systems supplying non-linear loads is that it allows for mitigation of power quality variations and events occurring from said loads in an efficient manner.
- the method may comprise the step of storing and processing data related to controlling and monitoring the active power filter in a cloud-based repository, wherein the machine learning component can be updated by downloading data stored in said cloud-based repository.
- a benefit of having a cloud based repository is that it allows for the method to be continuously updated and tuned by being connected to other devices in the cloud.
- an active power filter comprising a processor, at least memory, at least one input 106 and at least one output, wherein the processor is arranged to execute instruction sets for operating the method.
- a computer readable instruction set for controlling the output of an active power filter may be provided, the instruction set is arranged to perform the method.
- Figure 1 is a schematic block diagram illustrating an example of an active power filter device
- Figure 2 is schematic block diagram illustrating an exemplary processing and control unit for an active power filter
- Figure 3 is schematic block diagram illustrating an exemplary method for power quality events and variation compensation
- Figure 4 is schematic block diagram illustrating an exemplary method for power disturbance compensation
- Figure 5 is a schematic diagram of a machine learning component
- Figure 6 is a schematic diagram of self-programmable power electronic device.
- power quality refers to the ability of electrical equipment to consume the energy being supplied to it. There are several factors to power quality events and variations such as voltage sags, momentary power interruptions, electrical noise, ground loops, high-speed transients, flickers, inter-harmonics and harmonics.
- the power quality is influenced by the electric appliances connected to a power supply system such as a power grid.
- harmonics refers to a waveform whose frequency is a multiple of the fundamental frequency.
- the current shape will be distorted and harmonics may be introduced.
- non-linear loads are uninterrupted power suppliers, adjustable speed drives and electric arc furnaces. This may cause overheating or performance problems for equipment and loads in power systems.
- the distortion signals of harmonics may be compensated by injecting a compensation current with respect to the harmonics of the load. This may be performed by for instance an active power filter.
- harmonics refer to frequencies that can be observed between the harmonics of the power frequency voltage and current, further frequencies which are not an integer of the fundamental. They can appear as discrete frequencies or as a wide band spectrum.
- active power filter refers to a device having the purpose to compensate for power quality variations and events by injecting active power with the same frequency but reverse phase to cancel out the harmonics.
- Active power filters are developed for the compensation of time- and frequency-varying harmonic and interharmonic com ponents of loads with nonlinear and stochastic characteristics. These devices attempt to continuously detect the amplitudes and phases of the undesired frequency components and filter them out by supplying currents or voltages with the same amplitudes. In the case of power quality events and/or variations, the phases may be shifted by at least half-cycle for each component. Hence, each generated current or voltage component should be ideally out-of-phase and exactly at the same amplitude so that perfect com pensation is achieved.
- the active power filter may be directly connected to a grid or locally connected.
- Machine learning typically refers to computational structures that can be pro grammed automatically by a learning algorithm.
- An instance of such a structure with de fined and fixed parameters is referred to as a model.
- Machine learning is typically data-driven, meaning that it is achieved through the obser vation of data samples.
- each data sample is a pair of the form (x; y) where x is the input and y is the desired output of the model, known as the label.
- the model is altered in away so that the output will be more similar to the labels when given the corresponding inputs.
- pre-processing refers to a method of processing or restructuring the data in order to extract features for further processing or prediction.
- modified synchronous reference frame refers to a method of analysis that may be used in the pre-processing step to obtain both positive and negative se quences of d, q, and zero components of harmonics and inter-harmonics, as well as the fundamental component.
- the term “exponential smoothing” refers to a method used to estimate the DC variation of the data to obtain a low-pass filtered form of the positive and negative sequences of the d and q components of the frequency components.
- the disclosure relates to an active power filter device 100, comprising a processing and control unit 201 , at least one memory 202, at least one input 106 and at least one output 107, where the processing and control unit 201 is arranged to execute instruction sets for operating a method.
- Figure 1 discloses an active power filter device 100 comprising a processing and control unit 201.
- the active power filter device 100 may be in connection to a load 101 being at least partially supplied by a power supply system.
- the active power filter device 100 may be connected to a cloud-based repository 102 allowing for all processed and measured data to be stored in a centralized external server 105 in connection to a database 101. This may allow for all measured and processed data on an active power filter device 100 to be stored and used for large- scale optimisation to solve general high computational problems that benefit multiple devices. Accordingly, the cloud based repository 102 may further also transmit stored or processed data and other information to individual active power filter devices 100 connected to the cloud based repository 102. As seen in figure 1 the active power filter device 100 may be connected to an external device located remotely to the device, e.g. in a global network or a cloud-based repository 102 allowing for updates of instructions/instruction sets and/or data. The active power filter device 100 may further comprise an actuating device allowing for actuation of switching strategies.
- the processing and control unit 201 of the active power filter device 100 is shown in more detail.
- the processing and control unit 201 may comprise at least one processor, at least one memory 202, at least one input interface 205, at least one output interface 206, and at least one communication interface 207.
- the processing and control unit 201 may comprise at least one pre-processing module 250, at least one machine learning component/module 260, and at least one actuate control module 270.
- the pre processing module 250 may process and perform the step of pre-processing 302 which will be further discussed herein.
- the at least one actuate control module 270 may control an actuating device allowing for execution of switching strategies in the active power filter 100.
- the processing and control unit 201 may for instance comprise a microprocessor, digital signal processor (DSP), graphical processing unit (GPU), embedded processor, field programmable gate array (FPGA), or ASIC (Application specific integrated circuit), or a combination of these.
- the memory (computer readable storage medium) 202 may be a non-transitory or transitory computer readable memory and arranged to store instructions or instruction sets for execution by the processing and control unit 201 and to store data. Instruction sets are preferably stored in a non-transitory memory such as solid state (SSD), magnetic disk drive storage, and optical storage such as CD, DVD, or Blu-ray, or persistent solid state memory technology such as flash memory or memory card.
- the storage unit may also comprise a combination of storage types.
- the method may be realized in a computer program product and/or stored in a computer-readable storage medium.
- the memory 202 may be non-transitory or transitory computer- readable storage medium which stores one or more programs configured to be executed by one or more processing and control units 201 of an electronic device with or without a display apparatus and one or more input devices.
- the computer program product may be pre-installed in the device or delivered on a storage medium such as for instance SSD, magnetic storage, optical storage, or delivered on a network connection as a signal with a suitable protocol, for instance Ethernet using Internet Protocol (IP) or wirelessly with suitable radio protocol such as cellular technologies or short or medium range local area network technologies for installation in the device.
- IP Internet Protocol
- a computer readable instruction set for controlling the output 107 of an active power filter device 100 the instruction set arranged to perform a method for controlling and monitoring an active power filter device 100 as will be described herein.
- the disclosure further relates to a method 300 for controlling and monitoring an active power filter device 100, comprising the steps of:
- a machine learning component further predicts 303 future current and voltage levels 104;
- the desired output 107 refers to the output wherein the power disturbances such as harmonics or interharmonics are at least partially compensated.
- the prediction 303 of future current and voltage levels allows for future power quality variations and to be de tected and mitigated with a fast response-time.
- the method shown in figure 3 may accurately predict 303 power quality variations and events within a significant time window on a power signal recorded from highly nonlinear high-voltage systems. Additionally, there is an improved compensation 305 accuracy compared to other predictive methods.
- the compensation step 305 of figure 3 may include the step of providing the predicted future current and voltage levels to the active power filter device 100, allowing for the desired output 107 to be obtained.
- Figure 3 discloses the method of controlling and monitoring an active power filter 100.
- Figure 3 discloses the steps of measuring 301 the signal i.e. it discloses the step of extracting and detecting current and voltage levels from a non-linear load 101.
- a voltage interface unit and a current interface unit may be utilized during the measurement step 301.
- the voltage and current levels may be measured in a predetermined measuring point.
- the measurement signals achieved in the measuring step 301 may further be pre-processed 302 and predicted 303.
- the predicted values may be reconstructed 304 i.e. an original waveform may be reconstructed 304 in order to be prepared to be fed/provided to the active power filter device 100 for injecting a compensation 305 as shown in the last step of the method disclosed in figure 3.
- a data acquisition (DAQ) unit may transform the values from analog to digital and may allow the current and voltage values to be digitized and used in the machine learning parts in the measurement step 301 of the method disclosed in figure 3.
- the machine learning component 260 may be arranged to detect power quality events and variations. Furthermore, the machine learning component 260 may predict 303 future values before the active power filter device 100 compensates 305 the harmonics and/or interharmonics. Also the active power filter device 100 may compensate 305 other power quality events and variations.
- the methods of power quality event and variation detection performed by a machine learning component 260 after pre-processing 302 may be at least one of time-domain or frequency-domain analysis.
- frequency-domain analysis power quality variations such as harmonics and inter-harmonics, and events, may be analysed by Discrete Fourier
- DFT Fast Fourier Transform
- FFT Fast Fourier Transform
- the pre-processing 302 may further comprise; performing a FFT, RDFT, DFT or any combination thereof. Further, sliding Discrete Fourier Transform may be used in order to detect harmonics and synchronize to act as an adaptive-harmonic compensator.
- TD Time-domain
- the frequency domain (FD) approach may predict 303 the future samples of the original load current and voltage frequency components.
- the machine learning component 260 after the pre-processing 302 step may use a time domain machine learning based method and/or a frequency domain machine learning based method to estimate and predict samples.
- time domain ML based approach an ML algorithm may predict 303 the future samples of a load 101 such as for instance an electric arc furnaces current waveform and then, MSRF + ES may be used as a part of the pre-processing to detect the harmonics and interharmonics.
- samples from power quality events and variations may be extracted using sliding DFT and further are followed by a machine learning algo rithm to predict 303 power quality events and variations such as harmonics and inter harmonics components.
- a benefit of accurately predicting 303 future samples is that it may significantly reduce response time of any estimation method. Furthermore, the re sponse time delay problem for the active power filter device 100 may be eliminated so that real-time operation may be possible. This is specifically powerful for highly time- and frequency-varying spectrum cases such as nonlinear-load currents.
- the machine learning based method 300 utilized in the disclosure may provide a method that essentially reduces compensation delay time of active power filter devices 100 to zero, by modelling and prediction 303 of the frequency components of the load current signal. Response and reaction times of the active power filter device 100 may be re prised to zero, by estimating the future samples of power quality variations and events such as the harmonics and interharmonics of the non-linear load currents, the algorithms may be applied in parallel for each frequency component using graphical processing units 201.
- the method 300 may extract demanded frequency domain component, whether it is a harmonic or an interharmonic at any desired resolution.
- the method may perform prediction on all of the frequency components of signal simultaneously.
- the pre-processing 302 step may further comprise the steps of;
- the MSRF+ES method is utilized to decompose the signal into the phases and amplitudes of its frequency components.
- the MSRF+ES algorithm may have a minimum possible response time of at least 1ms with a sampling rate of at least 25KHz, which corresponds to 512 samples/cycle for the fundamental frequency 50.0Hz, 1ms approximately equals to 25 samples
- the extracted and detected features from the pre-processing step 302 may be at least one of individual harmonics, inter-harmonics, fundamental frequency, flicker, and/or any other disturbances in the signals.
- the term “other disturbances” refers to other power quality events such as voltage fluctuations, voltage and current unbalance, high frequency voltage noise or any other events.
- the machine learning component 260 may predict 303 future voltage and current by computing the amplitude and/or phases of at least one of harmonics, inter-harmonics or fundamental frequency at different frequencies for at least one future cycle. Furthermore, the machine learning component 260 may predict 303 future voltage and current for less than one future cycle. Further, the machine learning component 260 may adjust the number of future cycles calculated when predicting 303 said future voltage and current.
- said machine learning component may predict 303 the future voltage and future current levels by computing the amplitude and/or phases of at least one of harmonics, inter-harmonics or fundamental frequency at different frequencies for an adjustable amount of cycles.
- the predict-ahead time is a parameter, which may introduce a trade-off between desired prediction 303 and compensation accuracy and response time, which may be adjusted by the user of the active power filter device 100, in other words the disclosure provides an adjustable prediction time horizon.
- the method allows for mitigation of active power filter reaction time delay.
- the machine learning component 260 may comprise of a structure capable of containing a learning algorithm, said learning algorithms being Artificial Neural Networks, Support Vector Machines, Decision Tree, Bayes Classifier or any combination thereof.
- the structure may be a computational structure.
- a type artificial neural networks that may be used is convolutional Neural Networks (CNN) or Long Short-Term Memory (LSTM) or a type of recurrent neural networks (RNN) or any combination thereof.
- CNN convolutional Neural Networks
- LSTM Long Short-Term Memory
- RNN recurrent neural networks
- LSTM units are composed of cells, which can model and remember non-linear and time- varing signal and automatically learn their pattern.
- LSTM may be used by the machine learning component 260 for prediction 303 and classification of time se ries data such as harmonics, interharmonics and raw current signal itself.
- An LSTM cell is a stateful operator that, based on the input at some time, computes an output 107 and updates its internal state.
- the input may be a current waveform segment or frequency components extracted from such a segment.
- a current from a load 101 may be seg mented and paired to a corresponding ground truth prediction. At least a part of the power supply system may supply at least one non-linear load 101.
- At least a part of the power supply system may supply electric arc furnaces or variable frequency drives.
- the disclosure may be specifically beneficial for electric arc furnaces.
- the power supply system may be a power grid supplying any non-linear load 101. Elec tric arc furnaces may result in highly nonlinear and stochastic load characteristics in the power supply system due to their operation principles.
- the method 300 may optionally further comprise a step of storing and processing data related to controlling and monitoring the active power filter device 100 in a network cloud-based repository 102. Accordingly, all the current and previous states of current and voltage signals across a power supply system may be stored and processed in the cloud-based repository 102. Further, all data related to pre-processing 302 such as the extraction and detection of features may also be stored and processed in the cloud- based repository 102. Further, the output 107 of the active power filter device 100 may be stored and processed in a cloud-based repository 102.
- the data may be analyzed and stored in order to use such data and analysis in other events/applications/devices, allowing for different power supply systems to make use of the data for a more efficient and proactive handling of power quality events with the help of machine learning components.
- FIG 1 data relating to all steps in the method may be stored in a cloud-based repository 102.
- the machine learning component 260 may be updated by downloading data stored in the cloud-based repository 102. This may help the machine learning component 260 to recognize patterns and previous data, and adjust the computing of the amplitude and/or phases of at least one of harmonics, inter-harmonics or fundamental frequency at differ ent frequencies for future cycles.
- Figure 2 discloses this where there is seen at least one machine learning component/module 260 in a process having an input interface 205 and an output interface 206.
- the output signal may be computed and may be trained/updated regularly to minimise the error of the output 205.
- the processing and control unit 201 may be using learning algorithms such as Artificial Neural Networks, Support Vector Machines, Decision Tree, Bayes Classifier or any combination thereof.
- the error of the output 206 may be computed by an oracle unit, which may depend on the input 205.
- the method 300 may be performed by further comprising a switch control strategy which is shown in figure 4.
- Figure 4 discloses a method 400 for controlling and monitoring an active power filter device 100, comprising the steps of:
- machine learning component 260 further predicts 303 future current and voltage levels 104;
- the generated switch control strategy is based on the predictions from the machine learning component 260.
- the processing and control unit 201 may further comprise a second machine learning component, provided for computing 404 a switch control strategy for the active power filter 100.
- An exemplary machine learning component 500 is outlined in Figure 5.
- the machine learning component 500 is provided an input 503 which is used by a model 501 to compute an output 504.
- the model 501 which can be an algorithm built on a mathematical model may be trained/updated regularly to minimise the error of the output 504.
- the error may be computed by an oracle unit 502, which may depend also on some external input 503 (e.g. observation of the environment, additional measurements within or outside the self-programmable power electronic device, list of known correct outputs for all inputs).
- the pre-processing steps, and the machine learning training (performed by a machine learning component) and inference may be run on dedicated processing hardware, such as a central processing unit, graphics processing unit, field programmable gate array etc for accelerated parallel computation and any other suitable calculation.
- dedicated processing hardware such as a central processing unit, graphics processing unit, field programmable gate array etc for accelerated parallel computation and any other suitable calculation.
- FIG 6 an exemplary application of a machine learning component 500 is shown in relation to a self-programmable power electronic device 600 which may be an active power filter 100.
- a modification of the switch control component in a wide range of power electronic devices 600 which in part comprise replacing the control component with a machine learning component 601 as seen in figure 5, which can automatically learn the optimal control strategy for the particular power electronic device 600.
- a power electronic device 600 may be a rectifier or an inverter, or an active power filter or any other device.
- the switching strategy is empirically altered automatically over time, and adapts to changes in the environment such as placement, nearby devices, and wear of device components. By monitoring and analysing how the switching behaviour changes over time it can be possible to predict lifetime of components and report potential future component failures.
- the power electronic device 600 can be equipped with a dedicated software component for modelling and predicting wear of the device hardware. Accordingly, the method 300 may be directed to controlling and monitoring any power electronic device 600.
- the power electronic device 600 may comprise a power electronic component 606 having an input 602 and an output 603, wherein the input 602, the output 605, and the power electronic component 606 may be controlled and monitored by a machine learning component 601.
- the solution may be reported to an external device located in an external network, e.g. a cloud based solution.
- an external device located in an external network
- e.g. a cloud based solution While online machine learning is performed in small scale on individual power electronic devices 600, large-scale optimisation can be done in centralized servers to solve general high-computational problems that potentially benefit multiple power electronic devices 600. The result from the centralised large-scale optimisation is broadcasted to individual power electronic devices 600 that may accept the new strategy or partially merge with the local model in order to continuously increase the performance.
- the control strategy is learned automatically by observing the signal on the grid and optimising the switching strategy with respect to the corresponding output of the inverter, which implies an implicit modelling of the grid.
- this apples to disturbances in the grid, such as harmonics and power quality events.
- the inverter may as such also learn to compensate such disturbances.
- each individual power electronic device 600 continuously solves the switching and compensation problem based on local grid observation, and shares potentially generally useful strategies/experiences with other power electronic devices 600, which can choose to incorporate the received knowledge.
- the size of a predict-ahead time is a parameter, which introduces the trade-off between desired prediction and compensation accuracy and response time, the solution of which depends on the application. The end-used can hence tune the response time of a power electronic device 600.
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SE1951080A SE544845C2 (en) | 2019-09-25 | 2019-09-25 | Machine learning active power filter control method and device |
PCT/SE2020/050891 WO2021061040A1 (en) | 2019-09-25 | 2020-09-23 | Active power filter controlled by machine learning and method thereof |
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