Semiconductor Losses Calculation of a Quasi-Z-Source Inverter with Dead-Time

A quasi-Z-source inverter (qZSI) belongs to the group of single-stage boost inverters. The input dc voltage is boosted by utilizing an impedance network and so called shoot-through (ST) states. In pulse-width modulations utilized for the qZSI, the dead-time is commonly omitted. However, unintended ST states inevitably occur as a result of this action, due to the non-ideality of the switching devices, causing the unintended voltage boost of the inverter and an increase in the switching losses. Hence, the implementation of the dead-time is desirable with regard to both the controllability and efficiency of the qZSI. This paper deals with the calculation of semiconductor losses of the three- phase qZSI with implemented dead time. An algorithm available in the literature was utilized for that purpose. The algorithm in question was originally proposed and applied for the qZSI with omitted dead-time, where the occurrence of unintended, undetected ST states combined with the errors in the switching energy characteristics of the insulated gate bipolar transistor (IGBT) provided by a manufacturer led to errors in the obtained results. However, these errors were unjustifiably ascribed solely to the errors in the switching energy characteristics of the IGBT. In this paper, a new, corrected multiplication factor is experimentally determined and applied to the manufacturer-provided IGBT switching energies. The newly-determined multiplication factor is expectedly lower than the one obtained in the case of omitted dead time. The loss- calculation algorithm with the new multiplication factor was experimentally evaluated for different values of the qZSI input voltage, the duty cycle, and the switching frequency

State Variables Estimation in Vector Controlled Induction Machines

U radu su analizirane strukture vektorskog upravljanja asinkronim motorom zasnovane na ulančenom toku statora i ulančenom toku rotora. Za ove upravljačke strukture napravljeni su odgovarajući simulacijski programi. Uzet je u obzir utjecaj pogreške procjene induktiviteta motora. Analiziran je utjecaj efekta zasićenja u željezu na statičke i dinamičke karakteristike asinkronog motora pri konstantnom ulančenom toku statora i konstantnom ulančenom toku rotora. Napravljena je usporedba struktura vektorskog upravljanja asinkronim motorom zasnovanih na magnetskom toku statora i magnetskom toku rotora. Simulirane su skokovite promjene reference elektromagnetskog momenta sa utjecajem pogreške u procjeni rasipnih induktiviteta i međuinduktiviteta i bez nje. Na laboratorijskom modelu motora u otvorenom regulacijskom krugu obavljena je procjena varijabli stanja, elektromagnetskog momenta i snage pomoću digitalno snimljenih napona i struja statora. Da bi taj postupak bio izvediv napravljen je programski algoritam u C jeziku za numeričku integraciju digitalno snimljenih napona i struja statora.Upotrebom programskog paketa MATLAB kreirani su odgovarajući digitalni filteri sa ciljem odstranjvanja šuma i parazitnih efekata. U radu se, također, nalazi i kratki pregled teorije digitalnih filtera i elemnti izbora digitalnih filtera. Postupak procjene varijabli stanja, također, je proveden pomoću odgovarajućih analognih sklopova. Matematički postupci sumiranja, integriranja i množenja izvedeni su upotrebom sklopova s operacijskim pojačalima i analognim množačima, a analogno filtriranje faznih napona statora asinkronog motora je obavljeno analognim filterom drugog reda. U ovom radu je pokazano da je analogni postupak procjene varijabli stanja asinkronog motora preporučljiv samo za stacionarne režime rada i za frekvencije osnovnog harmonika napona napajanja koje su manje od 10 Hz. Potreba za procjenjivanjem varijabli stanja pri nižim frekvencijama napona napajanja (kada utjecaj viših harmoničkih komponenti u naponu napajanja postaje značajan), digitalnim postupkom, može se riješiti na način da se komponente vaktora napona statora filtriraju analognim filterom, a zatim digitalno integriraju, zbrajaju, oduzimaju i množe. U šestom poglavlju je analizirana jedna od struktura vektorskog upravljanja asinkronim motorom bez mjernog člana brzine vrtnje. Predložena struktura vektorskog upravljanja se zasniva na teoriji adaptivne regulacije i teoriji observera uz istovremenu identifikaciju omskog otpora statora. Ova struktura vektorskog upravljanja se razlikuje od konvencionalne upravljačke strukture zasnovane na referentnom modelu s adaptivnim sustavom (MRAS) s obzirom na definiranje referentnog i adaptivnog sustava, te izbor brzine vrtnje koordinatnog sustava u kojem se opisuje matematički model. Kod konvencionalne regulacijske strukture zasnovane na referentnom modelu s adaptivnim sustavom se, uobičajeno, tzv. naponski model za procjenu magnetskog toka rotora koristi kao referentni model, a strujni kao adaptivni model. U ovom radu se naponski model promatrao kao adaptivni, a strujni kao referentni. U ovom radu je napravljen odgovarajući program za simulaciju zaleta i kočenja asinkronog motora sa istovremenom procjenom brzine vrtnje i identifikacijom omskog otpora statora.This paper analyses the vector control system based on rotor magnetic flux and vector control system based on stator magnetic flux. Corresponding simulation programs for these control systems has been made. Impact of errors on inductance estimation of the induction motor has been taken into account. Impact of saturation effect in iron on induction motor static and dynamic characteristics with constant stator magnetic flux and rotor magnetic flux have analysed. Comparison of vector control systems based on rotor magnetic flux and stator magnetic flux has been made. Step changes of electromagnetic torque reference value with and without estimation error on leakage inductance and mutual inductance has been simulated. In laboratory model of induction motor in open loop estimation of state variable, electromagnetic torque and electrical power using sampled stator voltages and currents has been made. For this method numerical algorithm in C language has been made. Using program MATLAB corresponding digital filters has been created for noise and reactive effects elimination. There is, in this paper, a short oversee of digital filter theory and base for choice of digital filters. Also, algorithm of state variable estimation has been made using analog circuits. Mathematical proceedings (summarizing, integration and multiplication) has been made using circuits that incorporate amplifiers and analog multiplicators. Analog filtering of phase voltages of stator has been made using second order analog filter. In this paper have demonstrated that analog algorithm of state variable estimation is recommendable only for stationary states and for base harmonic frequencies in supply voltage that are less than 10 Hz. Estimation of state variable by lower frequencies (when impact of higher harmonic components in supply voltage become significant), using digital algorithm, one can to solve by filtering stator voltage components using analog filter, and thereupon that components add, subtract and multiplier. Into six chapter have analysed some with sensorless vector control of induction motor. The proposed system is based on a flux observer and the adaptive control theory with simultaneously stator resistance identification. The proposed scheme is simpler that the conventional MRAS scheme because the proposed system is constructed in the synchronous reference frame and current model is used as a reference model and voltage model is used as a adaptive model. Conventional MRAS scheme use current model as a adaptive model and voltage model as a reference model. In this paper has been made simulation program for start and break of induction motor with simultaneously stator resistance identification

State Variables Estimation in Vector Controlled Induction Machines

U radu su analizirane strukture vektorskog upravljanja asinkronim motorom zasnovane na ulančenom toku statora i ulančenom toku rotora. Za ove upravljačke strukture napravljeni su odgovarajući simulacijski programi. Uzet je u obzir utjecaj pogreške procjene induktiviteta motora. Analiziran je utjecaj efekta zasićenja u željezu na statičke i dinamičke karakteristike asinkronog motora pri konstantnom ulančenom toku statora i konstantnom ulančenom toku rotora. Napravljena je usporedba struktura vektorskog upravljanja asinkronim motorom zasnovanih na magnetskom toku statora i magnetskom toku rotora. Simulirane su skokovite promjene reference elektromagnetskog momenta sa utjecajem pogreške u procjeni rasipnih induktiviteta i međuinduktiviteta i bez nje. Na laboratorijskom modelu motora u otvorenom regulacijskom krugu obavljena je procjena varijabli stanja, elektromagnetskog momenta i snage pomoću digitalno snimljenih napona i struja statora. Da bi taj postupak bio izvediv napravljen je programski algoritam u C jeziku za numeričku integraciju digitalno snimljenih napona i struja statora.Upotrebom programskog paketa MATLAB kreirani su odgovarajući digitalni filteri sa ciljem odstranjvanja šuma i parazitnih efekata. U radu se, također, nalazi i kratki pregled teorije digitalnih filtera i elemnti izbora digitalnih filtera. Postupak procjene varijabli stanja, također, je proveden pomoću odgovarajućih analognih sklopova. Matematički postupci sumiranja, integriranja i množenja izvedeni su upotrebom sklopova s operacijskim pojačalima i analognim množačima, a analogno filtriranje faznih napona statora asinkronog motora je obavljeno analognim filterom drugog reda. U ovom radu je pokazano da je analogni postupak procjene varijabli stanja asinkronog motora preporučljiv samo za stacionarne režime rada i za frekvencije osnovnog harmonika napona napajanja koje su manje od 10 Hz. Potreba za procjenjivanjem varijabli stanja pri nižim frekvencijama napona napajanja (kada utjecaj viših harmoničkih komponenti u naponu napajanja postaje značajan), digitalnim postupkom, može se riješiti na način da se komponente vaktora napona statora filtriraju analognim filterom, a zatim digitalno integriraju, zbrajaju, oduzimaju i množe. U šestom poglavlju je analizirana jedna od struktura vektorskog upravljanja asinkronim motorom bez mjernog člana brzine vrtnje. Predložena struktura vektorskog upravljanja se zasniva na teoriji adaptivne regulacije i teoriji observera uz istovremenu identifikaciju omskog otpora statora. Ova struktura vektorskog upravljanja se razlikuje od konvencionalne upravljačke strukture zasnovane na referentnom modelu s adaptivnim sustavom (MRAS) s obzirom na definiranje referentnog i adaptivnog sustava, te izbor brzine vrtnje koordinatnog sustava u kojem se opisuje matematički model. Kod konvencionalne regulacijske strukture zasnovane na referentnom modelu s adaptivnim sustavom se, uobičajeno, tzv. naponski model za procjenu magnetskog toka rotora koristi kao referentni model, a strujni kao adaptivni model. U ovom radu se naponski model promatrao kao adaptivni, a strujni kao referentni. U ovom radu je napravljen odgovarajući program za simulaciju zaleta i kočenja asinkronog motora sa istovremenom procjenom brzine vrtnje i identifikacijom omskog otpora statora.This paper analyses the vector control system based on rotor magnetic flux and vector control system based on stator magnetic flux. Corresponding simulation programs for these control systems has been made. Impact of errors on inductance estimation of the induction motor has been taken into account. Impact of saturation effect in iron on induction motor static and dynamic characteristics with constant stator magnetic flux and rotor magnetic flux have analysed. Comparison of vector control systems based on rotor magnetic flux and stator magnetic flux has been made. Step changes of electromagnetic torque reference value with and without estimation error on leakage inductance and mutual inductance has been simulated. In laboratory model of induction motor in open loop estimation of state variable, electromagnetic torque and electrical power using sampled stator voltages and currents has been made. For this method numerical algorithm in C language has been made. Using program MATLAB corresponding digital filters has been created for noise and reactive effects elimination. There is, in this paper, a short oversee of digital filter theory and base for choice of digital filters. Also, algorithm of state variable estimation has been made using analog circuits. Mathematical proceedings (summarizing, integration and multiplication) has been made using circuits that incorporate amplifiers and analog multiplicators. Analog filtering of phase voltages of stator has been made using second order analog filter. In this paper have demonstrated that analog algorithm of state variable estimation is recommendable only for stationary states and for base harmonic frequencies in supply voltage that are less than 10 Hz. Estimation of state variable by lower frequencies (when impact of higher harmonic components in supply voltage become significant), using digital algorithm, one can to solve by filtering stator voltage components using analog filter, and thereupon that components add, subtract and multiplier. Into six chapter have analysed some with sensorless vector control of induction motor. The proposed system is based on a flux observer and the adaptive control theory with simultaneously stator resistance identification. The proposed scheme is simpler that the conventional MRAS scheme because the proposed system is constructed in the synchronous reference frame and current model is used as a reference model and voltage model is used as a adaptive model. Conventional MRAS scheme use current model as a adaptive model and voltage model as a reference model. In this paper has been made simulation program for start and break of induction motor with simultaneously stator resistance identification

Advanced Control Techniques for Wind/Solar/Battery Systems

This Editorial summarizes the papers of the Special Issue entitled ‘Advanced Control Techniques for Wind/Solar/Battery Systems’ published in Energies. The Special Issue includes four scientific articles published in 2021 and 2022 in the field of quasi-Z-Source inverter control, photovoltaic energy conversion, battery charge control, wind turbine speed control, and solar irradiance prediction. New scientific achievements with experimental verifications of the achieved results are presented in all articles

State Variables Estimation in Vector Controlled Induction Machines

U radu su analizirane strukture vektorskog upravljanja asinkronim motorom zasnovane na ulančenom toku statora i ulančenom toku rotora. Za ove upravljačke strukture napravljeni su odgovarajući simulacijski programi. Uzet je u obzir utjecaj pogreške procjene induktiviteta motora. Analiziran je utjecaj efekta zasićenja u željezu na statičke i dinamičke karakteristike asinkronog motora pri konstantnom ulančenom toku statora i konstantnom ulančenom toku rotora. Napravljena je usporedba struktura vektorskog upravljanja asinkronim motorom zasnovanih na magnetskom toku statora i magnetskom toku rotora. Simulirane su skokovite promjene reference elektromagnetskog momenta sa utjecajem pogreške u procjeni rasipnih induktiviteta i međuinduktiviteta i bez nje. Na laboratorijskom modelu motora u otvorenom regulacijskom krugu obavljena je procjena varijabli stanja, elektromagnetskog momenta i snage pomoću digitalno snimljenih napona i struja statora. Da bi taj postupak bio izvediv napravljen je programski algoritam u C jeziku za numeričku integraciju digitalno snimljenih napona i struja statora.Upotrebom programskog paketa MATLAB kreirani su odgovarajući digitalni filteri sa ciljem odstranjvanja šuma i parazitnih efekata. U radu se, također, nalazi i kratki pregled teorije digitalnih filtera i elemnti izbora digitalnih filtera. Postupak procjene varijabli stanja, također, je proveden pomoću odgovarajućih analognih sklopova. Matematički postupci sumiranja, integriranja i množenja izvedeni su upotrebom sklopova s operacijskim pojačalima i analognim množačima, a analogno filtriranje faznih napona statora asinkronog motora je obavljeno analognim filterom drugog reda. U ovom radu je pokazano da je analogni postupak procjene varijabli stanja asinkronog motora preporučljiv samo za stacionarne režime rada i za frekvencije osnovnog harmonika napona napajanja koje su manje od 10 Hz. Potreba za procjenjivanjem varijabli stanja pri nižim frekvencijama napona napajanja (kada utjecaj viših harmoničkih komponenti u naponu napajanja postaje značajan), digitalnim postupkom, može se riješiti na način da se komponente vaktora napona statora filtriraju analognim filterom, a zatim digitalno integriraju, zbrajaju, oduzimaju i množe. U šestom poglavlju je analizirana jedna od struktura vektorskog upravljanja asinkronim motorom bez mjernog člana brzine vrtnje. Predložena struktura vektorskog upravljanja se zasniva na teoriji adaptivne regulacije i teoriji observera uz istovremenu identifikaciju omskog otpora statora. Ova struktura vektorskog upravljanja se razlikuje od konvencionalne upravljačke strukture zasnovane na referentnom modelu s adaptivnim sustavom (MRAS) s obzirom na definiranje referentnog i adaptivnog sustava, te izbor brzine vrtnje koordinatnog sustava u kojem se opisuje matematički model. Kod konvencionalne regulacijske strukture zasnovane na referentnom modelu s adaptivnim sustavom se, uobičajeno, tzv. naponski model za procjenu magnetskog toka rotora koristi kao referentni model, a strujni kao adaptivni model. U ovom radu se naponski model promatrao kao adaptivni, a strujni kao referentni. U ovom radu je napravljen odgovarajući program za simulaciju zaleta i kočenja asinkronog motora sa istovremenom procjenom brzine vrtnje i identifikacijom omskog otpora statora.This paper analyses the vector control system based on rotor magnetic flux and vector control system based on stator magnetic flux. Corresponding simulation programs for these control systems has been made. Impact of errors on inductance estimation of the induction motor has been taken into account. Impact of saturation effect in iron on induction motor static and dynamic characteristics with constant stator magnetic flux and rotor magnetic flux have analysed. Comparison of vector control systems based on rotor magnetic flux and stator magnetic flux has been made. Step changes of electromagnetic torque reference value with and without estimation error on leakage inductance and mutual inductance has been simulated. In laboratory model of induction motor in open loop estimation of state variable, electromagnetic torque and electrical power using sampled stator voltages and currents has been made. For this method numerical algorithm in C language has been made. Using program MATLAB corresponding digital filters has been created for noise and reactive effects elimination. There is, in this paper, a short oversee of digital filter theory and base for choice of digital filters. Also, algorithm of state variable estimation has been made using analog circuits. Mathematical proceedings (summarizing, integration and multiplication) has been made using circuits that incorporate amplifiers and analog multiplicators. Analog filtering of phase voltages of stator has been made using second order analog filter. In this paper have demonstrated that analog algorithm of state variable estimation is recommendable only for stationary states and for base harmonic frequencies in supply voltage that are less than 10 Hz. Estimation of state variable by lower frequencies (when impact of higher harmonic components in supply voltage become significant), using digital algorithm, one can to solve by filtering stator voltage components using analog filter, and thereupon that components add, subtract and multiplier. Into six chapter have analysed some with sensorless vector control of induction motor. The proposed system is based on a flux observer and the adaptive control theory with simultaneously stator resistance identification. The proposed scheme is simpler that the conventional MRAS scheme because the proposed system is constructed in the synchronous reference frame and current model is used as a reference model and voltage model is used as a adaptive model. Conventional MRAS scheme use current model as a adaptive model and voltage model as a reference model. In this paper has been made simulation program for start and break of induction motor with simultaneously stator resistance identification

Dynamic model of a self-excited induction generator with fundamental stray load and iron losses

This paper considers a dynamic model of a self-excited induction generator that takes into account the fundamental stray load and iron losses. The model is de¬scribed with the same number of differential equations as the conventional induc¬tion machine model. Determination of the stray load and iron losses resistances does not involve any tests other than those imposed by the international standards nor does it require any details about induction machine materials or geometry. The dynamic analysis has been carried out for the case of a wind turbine-driven self-excited induction generator. The steady-state analysis, on the other hand, has been carried out for the case of a load-independent prime mover. The considered advanced model, aside from being compared with the conventional model, has been experimentally validated for two different-efficiency induction machines, both rated 1.5 kW

Hybrid Wind-Solar Power System with a Battery-Assisted Quasi-Z-Source Inverter: Optimal Power Generation by Deploying Minimum Sensors

This paper presents a hybrid renewable energy system (RES) including wind and photovoltaic (PV) power sources. The wind energy subsystem (WES) consists of a squirrel-cage induction generator (SCIG) driven by a variable-speed wind turbine (WT) and corresponding power electronic converter, by means of which a speed-sensorless indirect-rotor-field-oriented control of the SCIG is implemented. The outputs of both the WES and PV power source rated 1.5 kW and 3.5 kW, respectively, are connected to the DC bus, with the quasi-Z-source inverter (qZSI) acting as an interlinking converter between the DC bus and the AC grid/load. An advanced pulse-width-modulation scheme is applied to reduce the qZSI switching losses. The considered RES can operate both in grid-tie and island operation, whereas the battery storage system—integrated within the qZSI impedance network—enables more efficient energy management. The proposed control scheme includes successively executed algorithms for the optimization of the WES and PV power outputs under varying atmospheric conditions. A perturb-and-observe PV optimization algorithm is executed first due to the significantly faster dynamics and higher-rated power of the PV source compared to the WES. The WES optimization algorithm includes two distinct fuzzy logic optimizations: one for extraction of the maximum wind power and the other for minimization of the SCIG losses. To reduce the number of the required sensors, all three MPPT algorithms utilize the same input variable—the qZSI’s input power—thus increasing the system’s reliability and reducing the cost of implementation. The performance of the proposed hybrid RES was experimentally evaluated over wide ranges of simulated atmospheric conditions in both the island and grid-tie operation

Experimental Investigation of a Standalone Wind Energy System with a Battery-Assisted Quasi-Z-Source Inverter

This paper presents a wind energy conversion system (WECS) for grid-isolated areas. The system includes a squirrel-cage induction generator (SCIG) and a battery-assisted quasi-Z source inverter (qZSI). The batteries ensure reliable and stable operation of the WECS in spite of the wind power oscillations. The maximum power is captured from both the wind turbine (WT) and the SCIG through adjustment of the WT speed and the SCIG operating flux, respectively. The utilized maximum power point tracking (MPPT) algorithms belong to the group of fuzzy logic (FL) search-based algorithms. The battery state of charge (SOC) is tracked online and controlled. When it reaches the minimum allowed level, the load is automatically disconnected; conversely, when it reaches the maximum allowed level, the battery charging is stopped via WT speed control. The load voltage root-mean-square (RMS) value and frequency are at all times controlled at grid-level values. The performance of the proposed system was experimentally validated, in steady state and during transients, achieving wide ranges of wind speed, load power, SOC, and alternating current/direct current (AC/DC) voltage levels. The system startup and low-wind operation were also analyzed. The control algorithms were executed in real time by means of the DS1103 and MicroLabBox controller boards (dSpace)

Photovoltaic System with a Battery-Assisted Quasi-Z-Source Inverter: Improved Control System Design Based on a Novel Small-Signal Model

This paper deals with a photovoltaic (PV) system containing a quasi-Z-source inverter (qZSI) and batteries connected in parallel with the qZSI’s lower-voltage capacitor. The control system design is based on knowledge of three transfer functions which are obtained from the novel small-signal model of the considered system. The transfer function from the d-axis grid current to the battery current has been identified for the first time in this study for the considered system configuration and has been utilized for the design of the battery current control loop for the grid-tied operation. The transfer function from the duty cycle to the PV source voltage has been utilized for the design of the PV source voltage control loop. The PV source voltage is controlled so as to ensure the desired power production of the PV source. For the maximum power point tracking, a perturb-and-observe algorithm is utilized that does not require the measurement of the PV source current, but it instead utilizes the battery current during the stand-alone operation and the d-axis reference current during the grid-tied operation. The corresponding tracking period was determined by using the transfer function from the duty cycle to the battery current and in accordance with the longest settling time noted in the corresponding step response. The proposed control algorithm also has integrated protection against battery overcharging during the stand-alone operation. The considered system has been experimentally tested over wide ranges of irradiance and PV panel temperature

Calculation of Semiconductor Power Losses of a Three-Phase Quasi-Z-Source Inverter

This paper presents two novel algorithms for the calculation of semiconductor losses of a three-phase quasi-Z-source inverter (qZSI). The conduction and switching losses are calculated based on the output current-voltage characteristics and switching characteristics, respectively, which are provided by the semiconductor device manufacturer. The considered inverter has been operated in a stand-alone operation mode, whereby the sinusoidal pulse width modulation (SPWM) with injected 3rd harmonic has been implemented. The proposed algorithms calculate the losses of the insulated gate bipolar transistors (IGBTs) and the free-wheeling diodes in the inverter bridge, as well as the losses of the impedance network diode. The first considered algorithm requires the mean value of the inverter input voltage, the mean value of the impedance network inductor current, the peak value of the phase current, the modulation index, the duty cycle, and the phase angle between the fundamental output phase current and voltage. Its implementation is feasible only for the Z-source-related topologies with the SPWM. The second considered algorithm requires the instantaneous values of the inverter input voltage, the impedance network diode current, the impedance network inductor current, the phase current, and the duty cycle. However, it does not impose any limitations regarding the inverter topology or switching modulation strategy. The semiconductor losses calculated by the proposed algorithms were compared with the experimentally determined losses. Based on the comparison, the correction factor for the IGBT switching energies was determined so the errors of both the algorithms were reduced to less than 12%