Phase shifting transformers (PSTs) are currently widely used in power systems to control power flow. In this manuscript, the results of the asymmetrical PST (APST) with the in-phase PST (called ...asymmetrical controllable PST-ACPST) were compared, allowing to control both longitudinal and quadrature voltage. The MATLAB simulation model of the ACPST was built to obtain influence of PST in selected models for selected parameters. Then the 30A laboratory PST device was built in the laboratory. The parameters of the MATLAB model were then adjusted to parameters of the real life PST model. This allowed verifying the results of the real life and computer simulations. Based on the ACPST simulation model, the APST model was built; for the given work conditions, the influence of both PSTs were compared. APST construction always resulted in higher output voltage than the input one. ACPST achieved the same power transfer for the lower output PST voltage, which is its main advantage. This dependency is a result of the greater ACPST angle compared to the classical APST. The ACPST also allowed adjusting longitudinal and quadrature voltages; therefore, this PST type can be installed in places where high flexibility is required, especially in systems with high renewable energy sources penetration.
The article presents the concept of application of a multiphase matrix converter (MMC)-based device working as a phase-shifting control device in a power system. A matrix M × M multiphase converter ...is a simple structure incorporating M × M bidirectional switches, connecting M input phases to M output phases (a square structure is used). The device, in this research and under proposed control, is able to build M output sinusoidal-shape phases (desired output) from parts of input voltages. The proposed MMC-based device can be considered as a new flexible AC transmission system (FACTS) apparatus. Three basic control systems that enabled the creation of output waveforms as the combination of input ones were presented. Both 6 × 6 and 12 × 12 matrix structures were introduced, since 3 × 6 and 3 × 12 transformers are already in use. The mathematical, Simulink, and laboratory models were built to extract characteristic features of the MMC. The chosen “area-based” control procedure was based on finding a common point of area representing a certain switch (connecting a certain input and a certain output) and a time-dependent trajectory. Practical application of the MMC in a power system involves not only MMC analysis, but also the study of application requirements, possible converter topologies, and the development of new, reliable control algorithms. Particular consideration was given to the simplicity of the control and the analysis of the converter properties. The proposed control procedure did not use the PWM technique, but created output in similar way to a multilevel converter.
This article was written to present a new solution for a phase-shifting transformer and to show that, in many aspects, the proposed device is more functional and improved when compared to the other ...currently available phase-shifting structures. The article shows the construction of the new phase-shifting transformer, with longitudinal and transverse voltage regulation. The proposed device’s functionality and available operation states are compared to other existing solutions. Selected steady-state variants of the operation of the proposed transformer were checked based on computer simulations and the laboratory model presented in detail in the article. Convergence between measurements and simulations was achieved. Power flow calculations were also performed in the five-node electrical power system model. In these calculations, two variants of the proposed device’s work were considered and compared with the asymmetric phase shifter. The tests confirmed in the proposed structure, both angle and voltage regulation, enabled maintaining a constant active power flow. The authors show that the proposed solution combines the advantages and functionality of various types of phase shifters while, at the same time, being characterized by a much simpler structure, which results in a two-times-lower cost of the device.
The article describes the application of a straight forward energy converter, a multiphase matrix converter (MC), as part of a device, connected parallel to the power grid, and able to supply ...variable reactive power flow to the power system. The research performed by authors included the development of control procedures for a multiphase MC, based on a new approach and power system (application) requirements. The multiphase MC structure (6 × 6, 12 × 12) was used since the proposed control procedure creates output as the combination of input voltages. The increased number of phases decreases the order of harmonics in the MC converter similarly as in multilevel converters. This manuscript concentrates on the mathematical analysis of MC work under the “one periodical” algorithm and links it introduces in the power system. The previously developed, spatial-temporal mathematical model of the MC was limited to the dominant (first) harmonic and applied between the grid and reactive load. The results obtained from the analysis of the model showed that, for the applied control procedure (one periodical algorithm), the output voltage is built only from positive or negative sequences of input voltage. Three cases were recognized where the sign input power factor depends on input voltage and control sequence as well as on the value of control frequency. The effects of the model simulation were compared to those obtained from the MATLAB simulation and from the real laboratory 30 kVA-rated model. The main factors analyzed during this research include the expected value and distortion of input current and sign of reactive input power.
•Recognition of the anti-shock protection problems in power supply systems fed from auxiliary sources.•Assessment of the tripping effectiveness of miniature circuit breakers (MCB).•Development of new ...class of the protection devices based on voltage and current measurements.•Commissioning and tests of the device in the laboratory.
Due to the supply reliability concerns or to supply remote loads in some distribution networks, the synchronous generators are used as auxiliary power sources. In Poland the generators are usually connected to the network of TN (earthed neutral point) structures. Both TN-C and TN-S or their mixed arrangements TN-C-S are used. Overcurrent protection in these circuits, according to Polish and international standards and the recommendation of SEP (Association of Polish Electrical Engineers), should also act as anti-shock protection. The protection is considered to be effective (for 400V electrical installations) if the overcurrent protection trip takes less than 0.4s (maximum allowable time of touching voltage occurrence). The investigation performed by authors, showed that the producers of the generators usually use B or C characteristic circuit breakers and for large generator sets (greater than 100kVA) they recommend load split to the value of one fifth of the generator maximum power. Additionally, the most frequently excitation forcing equipment is mounted to keep short circuit current three times greater than nominal current of the generator. To assess the effectiveness of the anti-shock protection measures in circuits fed from auxiliary generator and for current lower than 32A, the set up including a self-exiting 5.5kVA and 400V generator, overcurrent protection and load was built in laboratory. The set up uses miniature circuit breakers and enables short circuits in different instants, compared to the initial phase angle of the generator voltage.
of the performed short circuits showed, that for the self-excited generators (majority of small generator sets with stator current lower than 32A) the overcurrent protection cannot act as anti-shock protection, when breakers allowing full utilisation of the generator power. The alternative is to limit generator load or to introduce excitation forcing increasing device price. The proposed solution for these generators given by authors is to modify anti-shock protection system in such way, that the tripping occurs always in the time below 0.4s. Modifications include not only introduction of the measurements of currents, but also the measurements of the generator voltage. The short circuit is indicated not only by current increase, but also by voltage drop during short circuit.
device utilizing both measurements was build and tested for different initial short-circuit instants, with respect to the synchronous generator phase voltages. In every case, the switch-off time of the short circuit was not longer than 0.4s, what means that the protection against the risk of electric shock was effective. The settings of the device are fully adjustable, what means that levels of the measured quantities indicating trip as well as the reaction time are adjustable.
The article is a review of the latest available technologies on the market which are part of “Industry 4.0”, in the field of protection, control, and power supply of equipment. The authors focus on ...the development of the protection devices (PLC controllers), which can be used not only for protection purposes but also for the diagnosis and monitoring of the entire system. The key element is the communication structure involving protection, main PLC controller, and DCS, which has an impact on the reliability of the whole system. The authors compare different solutions that allow increasing the reliability of the system (ethernet connection), compared to the classic system (wire connection). Universal protection devices are more flexible devices compared to classic control equipment, but also allow us to make modifications to the structure after commissioning, during normal operation of the system without stopping the technological process.
This paper presents an analysis of the application of a multi-phase matrix converter (PM) based device as a phase shifter (PS). The analysis was conducted using simulation techniques and measurements ...performed on a six-phase converter model built in a laboratory. Three basic control schemes and their relation to PM properties are presented. In addition to the phase shifter’s ability to change active power transfer, the device’s impact on reactive power transmission was also shown in the paper. Newly assessed PM properties permit the construction of a PS with higher power system control capacity than with currently available devices. Capabilities of various variants of PM control and fast rate of response of the PS based on it, will undoubtedly be useful in the control of dynamic states of the power system operation (postdisturbance states), e.g. for rapid elimination of generator oscillations or power flow adjustment. This study is an extension of the phase shifter concept presented in previous years, and the continuation assumes the construction of a shifter model for use in an already developed at Cracow University of Technology power system model.
The article presents the concept of new matrix converter (MC) based device working as a phase shifting control device in a power system. The multiphase MC is working under an innovative control ...algorithm specially dedicated to the proposed application. The work presents the results of the simulation of the MC work in this application as well as the analysis of the MC properties.
The paper analyses the effectiveness of the human protection against electric shock in circuits fed from the generator, especially from the backup generation set. Several protection devices of ...different characteristics were tested in laboratory and new approach to the protection was proposed in TN type wiring (earthed neutral point arrangement). This happened due to the fact that measurements showed that actually used devices do not satisfy protection criteria when full power of the generator is used. This criteria include time criterion - the maximum time of the occurrence of touching overvoltage can occur in less than 0.4 s time period. The proposal include new approach to the short circuit detection, where not only current but also voltage sensing is used. For a IT wiring (system insulated from the ground) " 0 " symmetrical component sensing an insulation testing devices are proposed.
Multiphase matrix converter for grid applications Szczepanik, Jerzy; Sienko, Tomasz
2018 IEEE 12th International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG 2018),
2018-April
Conference Proceeding
The increases in size and transmission capabilities of modern power grids as well as the escalation of their penetration by variable and poorly controlled electrical energy sources generate problems ...with control of power flow within lines of supply network. The regulation of power flow through the transmission line requires the control of its end voltages (values and difference of their angles), The values of the voltage are relatively easy to control, however the change of the node voltage angle requires costly and complicated equipment (phase shifting transformers or FACTS devices). Presented research introduces the straight-forward, matrix converter based, energy conversion device to the power grid as a voltage phase shifter. The paper gives a solution to the control system of the multiphase matrix converters, states real-life application requirements (power system), proposes possible converter topologies and analyses properties of the developed device on basis of simulation and laboratory model results.
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