Annotation of the results obtained in 2023
1. During the work on the project, new digital algorithms for controlling an energy storage device based on a DC/DC converter with a block of supercapacitors were obtained, which were then implemented in an experimental setup using microprocessor technology. A new algorithm has been proposed that will smooth out the peak loads in the energy supply system. The performance of the developed algorithm is confirmed by mathematical simulation methods, as well as experimental studies. 2. Complex, digital models of variable frequency drive systems with an energy storage device have been developed, which take into account the discrete properties of a bidirectional DC/DC converter as a control object, the presence of noise in the measured variables, as well as level and time quantization in the microprocessor implementation of control algorithms. As a result of testing the developed control algorithms, conclusions were drawn about a good agreement between the results obtained from mathematical modeling and experimental studies. Simulation and experimental evaluation results of digital single-loop control system of a supercapacitor energy storage system have validated the following statements: - The possibility of current controller synthesis from the averaged model of the power converter for supercapacitor energy storage device; - The using of tuning of continuous control system to modulus optimum with the subsequent transition to the digital approximation; - The functioning of the digital single-loop automatic control system with satisfactory performance. 3. The authors proposed a new approach for selecting the storage capacity to smooth out peak loads, based on the setting of the peak current, which is consumed from the contact power supply. The dependence of the supercapacitor capacitance on the peak current was obtained. An example of determining the capacity of a supercapacitor module for a variable-frequency electric drive of a tram is considered. When assessing the estimated cost of an energy storage system for an electric tram drive, it is shown that the proposed approach can reduce the cost of a supercapacitor unit by up to 10 times and the cost of the entire energy storage system by up to 3 times. 4. The authors have determined a rational application area for electric drive systems with smoothing of peak loads based on supercapacitors. Among the rational applications of an energy storage system for smoothing peak loads, after a detailed analysis of domestic and foreign literature, the authors highlight the urban electric transport systems, as well as powerful electric drive systems, which work in “weak” power supply networks, and operating in intensive starting-braking operating modes. 5. In the peak power smoothing algorithm a strategy for pre-charging the supercapacitor in motor operating modes of an electric drive and a mechanism for charging from the load during operation in braking modes of asynchronous motors were proposed. The basic idea of the supercapacitor bank pre-charge strategy is that the pre-charge mode is carried out when the inverter current does not exceed the maximum peak current value and the voltage on the supercapacitor bank has not reached the maximum. Recommendations for selecting the precharge current value are given. Moreover, in the proposed algorithm, to increase the energy efficiency of the system when the electric drive operates in braking modes, charging is carried out using the kinetic energy, stored in the rotating parts of the electric drive. 6. While working on the project, an experimental setup was designed and implemented to test the developed control algorithms. The experimental setup includes a power source, a passive load and a capacitive electrical energy storage device. In the lab test bench, the control module algorithms are implemented on a Texas Instruments LAUNCHXL-F28379D development kit with a TMS320F28379D microcontroller. The development board includes ADCs with switchable 12 and 16 bit resolution with up to 3.5 million samples per second per ADC in 12 bit mode. The ADCs, used in the experimental bench, were in 12-bit resolution mode with 200 kHz synchronized sampling rate. Direct memory access (DMA) and serial asynchronous (SCI/UART) and synchronous (SPI) digital interface modules on the development board were used to transfer telemetry data to a PC and receive reference signal values. The telemetry data transfer rate to the PC is up to 20 MBit/s. The development board also features the XDS100v2 integrated programmer with galvanic isolation, which includes an auxiliary UART interface with a baud rate of up to 12 MBit/s. The FT232H universal interface converter, operating in SPI Master mode, is used to transmit telemetry data with a data rate of 20MBit/s. Telemetry is transmitted via a HCPL-092J galvanic isolator integrated circuit. On the PC side, a graphical interface for control and monitoring is implemented, based on the GNU Radio software package, used for processing large volumes/streams of data in real time. While working on the project, a new method for experimental research of digital control algorithms for a bidirectional DC/DC converter was proposed. The peculiarities of the technique are that it allows you to fully test the operation of a digital control system without using an electric drive, as well as at low voltage levels. 7. When assessing the effectiveness of the developed algorithm for reducing peak loads for urban electric transport systems, it was shown, that the using an energy storage system with a peak power smoothing function can lead to decreasing in the required power of the DC contact network. This provision can be extrapolated to variable frequency drive systems, where the using of this system may result in a reduction in the required power of input rectifier. 8. While working on the project, recommendations were received for integrating energy storage systems with a peak load smoothing function into existing variable frequency drive systems.

 

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Annotation of the results obtained in 2022
1. A review and analysis of the literature has been carried out, which allows to solve the problems of choosing and optimizing the parameters of electric energy storage devices for electric transport systems and industrial electric drive systems. The presented review of literature shows, that the using of supercapacitor energy storage systems in the frequency-controlled electric drives, the operating cycle of which is characterized by presence the starting and braking operation modes, is the effective way to improve its technical and economic characteristics. The energy efficiency of such electric drives can be improved by using combined power sources consisting of energy and power sources. The energy source covers the power, consumed in the steady state operation of the drive, and the power source covers the peak energy consumption at the start-up modes of electric drive and receives energy, coming from the motor during braking. In circuit solutions of combined power supplies, the role of a power source is provided by supercapacitors, the charging/discharging of which is often controlled by means of bidirectional DC/DC converters. Combined power sources with a supercapacitor energy storage system, compared to traditional power sources, allow to eliminate the oversizing of installed power for energy source (diesel generator, battery, fuel cell), to reduce the energy (fuel) consumption, to increase the service lifetime of the main energy source and efficiency of whole electric drive system. The using of energy storage systems based on supercapacitors, in addition to energy saving, also allows to solve a number of other problems: • with appropriate control of energy flow distribution, it is possible to smooth the power consumption peaks from the main energy source; • it is possible to provide the voltage level stabilization of the main source during changing the load of electric drive; • reduction of operating costs is provided; • it is also possible to avoid the problem with power supply quality, which is occurred if the regenerating energy is fed into the local power supply system. 2. New algorithms have been developed for automatic control system of energy storage device based on a bidirectional DC-DC converter and a supercapacitors block, which increase the accuracy of voltage stabilization in the DC link of the frequency converter. The developed algorithms can be used in variable frequency drive systems with energy storage devices, which provide a reduction the peak loads on the power supply system. The problem of the voltage stabilization in the DC link of a frequency converter with a PWM inverter, which is part of AC drive with a frequency method of speed control, was considered. To stabilize the voltage in the DC link, energy storage technology is used, which is implemented with using an energy storage device based on supercapacitors, which is connected to the DC link by means of bi-directional DC-DC converter. During the solving the problem of voltage stabilization the concept of stabilizing the DC bus voltage by compensating the PWM inverter load current with the external current of the energy storage device was used. The energy storage device is equipped with a single-loop tracking current control system. The current control system is based on the combined control method. The sensitivity of the DC link voltage to various disturbing factors is investigated. The theoretical analysis of the error coefficient of the current control system is carried out. The simulation of the electric drive is carried out without and taking into account the discreteness of the DC-DC converter. The research results can be useful in the development of supercapacitor energy storage control systems for various applications. 3. In the first year of work on the project, preliminary work on the preparation of experimental setup for testing and verifying the developed digital control algorithms was carried out. In particular, the concept of an experimental setup, which involves the use of a single TMS320F28379D processor to control both a frequency-controlled electric drive and a DC / DC converter as part of an energy storage device, was proposed. This approach will allow us to simultaneously receive and analyze the transient processes in a frequency-controlled electric drive and an energy storage device. The PowerCard-03V2.3 module manufactured by Mechatronika-Pro is used as the power part of the frequency-controlled electric drive in the experimental setup. The power part of the DC/DC converter will be made based on silicon carbide MOSFET transistors SCT30N120, which will make it possible to obtain a pulse-width modulation frequency of up to 30 kHz. A high PWM frequency will reduce the weight and size of the inductance. To work with the stand, software, that allows to control the main functions of the installation, change the main parameters of the frequency converter and DC / DC converter, as well as take graphs of transients, was developed.

 

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