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A Three-Phase UPS That Complies With the Standard IEC 62040-3

This paper proposes a down-sampled discrete-time internal-model-based controller in the synchronous reference frame with a reduced number of poles. This controller is suitable for three-phase pulsewidth modulation inverters with output transformer for double-conversion uninterruptible power supply applications. It is demonstrated that the use of a down-sampled rate and fewer poles in the internal model results in a number of benefits, among which are the following: 1) improvement of the transient response; 2) increase of the stability margin of the closed-loop system; 3) a straightforward implementation in fixed-point digital signal processor (DSP) and microcontroller implementation as well as a reduction of the required memory space; and 4) a simple solution for the saturation of the output transformer. As a result, it is possible to obtain output voltages with reduced total harmonic distortion while ensuring good transient performance for both linear and nonlinear loads. To confirm the advantages claimed for the proposed synchronous reference dq frame internal-model-based controller and to demonstrate the steady-state and transient performance under the test conditions of the International electrotechnical commission standard 62040-3, the experimental results from a 10-kVA space-vector-modulated three-phase inverter, which is fully controlled by a DSP TMS320F241, are presented.

A digital controller for single-phase UPS inverters to reduce the output DC component

This paper proposes a new two layers digital controller for PWM inverters, which significantly reduces the output DC voltage component. It is suitable for low cost PWM inverters where analog-to-digital converters and digital pulse width modulators with small numbers of bits are used. The controller description and design are presented. Experimental results on a 5 kVA set-up validate the theoretical analysis carried out.

Modulação space vector para inversores alimentados em tensão: uma abordagem unificada

This paper presents a unified approach of the space vector modulation for voltage-source inverters. To demonstrate the proposed unified approach, five fundamental inverters topologies are analyzed, that are: single-phase full-bridge; three-phase three-wire; three-phase four-wire, three-phase four-leg and three-phase three-level inverters. Switching vectors, separation and boundary planes in the inverter output space as well as decomposition matrices and possible switching sequences are derived for each one of these inverters. Experimental results are shown to validate the proposed approach.

Metodologia de projeto de filtros de segunda ordem para inversores de tensão com modulação PWM digital

This paper presents a systematized methodology of second-order output filter for inverters that synthesize sinusoidal voltage waveforms through digital pulse-width modulation (PWM). The objective of this methodology is to determine the largest corner frequency of the filter that ensure the specification of the maximum total harmonic distortion (THD) admissible in the output voltages of the PWM inverter, for linear and non-linear loads. The proposed methodology is discussed in detail, including the description of the required steps for the derivation of the design procedure for different topologies of voltage inverters and the procedure to obtain the design curve. Finally, it is presented some design examples for single-phase, three-phase three-wire and three-phase four-wire filters topologies. Experimental results have been provided to demonstrate the validity of the proposed design methodology.

Discrete-time adaptive control applied to voltage regulation of induction generator based systems

This paper deals with the development of an adaptive control system applied to voltage regulation of a standalone distributed power generation system, fed by self-excited induction generator. The generation system considers a four wire three-phase grid, composed by three phases plus neutral conductor, fed by three-phase three wires induction generator. The neutral conductor is created from the neutral point of star connection of excitation capacitors. The four-wire configuration allows the connection of three-phase loads in star or delta configuration, as well as single-phase loads. The voltage regulation is performed through a four-legs distribution static compensator (DSTATCOM) shunt connected to the AC bus. The adaptive controller proposed offers suitable voltage regulation in conditions of systems parameters variations such as, load connection and disconnection, and changes in induction generators unmodeled parameters. The proposed generating system was simulated in MATLAB, where simulation results were obtained to show the good performance of the voltage regulation control system during the connection and disconnection of three-phase loads. Additionally, some preliminary experimental results are presented as well.

Improved State-Variable Internal Model Based Digital Controller for Three-Phase PWM Inverters that Complies with the Standard Iec 62040-3

This paper proposes an improved state-variable internal model based digital voltage controller suitable for three-phase PWM inverters with output transformer for medium and high power uninterruptible power supplies (UPS). The proposed controller is derived from the internal model principle using a state-variable approach in stationary alfa-beta frame. For the controller design an improved discrete-time model that uses the average of two samples in a switching period is proposed. In addition, this model takes into account the digital implementation time delay. With the proposed controller it is possible to obtain a high performance in both steady-state and load transients. Also, with the selected internal model, dc components resulting from the circuit implementation non-idealities are not amplified, avoiding transformer saturation. To validate the proposed digital controller and to demonstrate the steady-state and transient performance, experimental results from a 10kVA space vector modulated three-phase inverter, fully controlled by a DSP TMS320F241, are presented. In steady-state the UPS output voltages have very low total harmonic distortion (THD) for both balanced and unbalanced non-linear loads. The output voltage dynamic performance complies with the international Standard IEC 62040-3 Classification 1, which is the most severe limit making the three-phase PWM inverter suitable for most types of critical loads.

A Three-Phase PWM Inverter For Double Conversion UPS That Complies With the Standard IEC 62040-3

This paper proposes an improved digital voltage controller suitable for three-phase PWM inverters with output transformer for medium and high power uninterruptible power supplies (UPS). The proposed controller is derived from the internal model principle using a state-variable approach in stationary alphabeta frame. With this controller it is possible to obtain a high performance in both steady-state and load transients. In addition, with the selected internal model, DC components result from real circuit implementation non-idealities are not amplified avoiding in this way, the transformer saturation. The UPS output voltages have reduced total harmonic distortion (THD) for both balanced and unbalanced non-linear loads. Regarding the transient performance, load steps responses are improved with the proposed digital controller and as a result the UPS compliant with the classification 1 of the international standard IEC 62040-3. In order to validate the proposed digital controller and to demonstrate the steady-state and transient performance, experimental results from a 10 kVA space vector modulated three-phase inverter, fully controlled by a DSP TMS320F241, are presented

Novos algoritmos de limitação para inversores de tensão PWM a quatro braços utilizando modulação space vector

This paper proposes two novel limiting algorithms for three-phase four-leg voltage source inverters to constrain the command vector inside the dodecahedron defined by the boundaries of the inverter linear operating range. The first algorithm uses an inscribed ellipsoid on the dodecahedron, and the second one is based on the polyhedron boundary planes. A detailed description, with the key points required for a digital implementation of space vector and limiting algorithms, is given. In addition, the output voltages and the inductors currents are dynamically regulated by means of MIMO servo controller in dq0 coordinates. These controllers are designed using optimal discrete linear quadratic regulator technique, which ensures stability for the system at all operating conditions. In order to provide smooth transitions among the different modes of operation, nonlinear MIMO anti-windup algorithms are proposed to dynamically update the controllers servo variables. Finally, experimental results on a 15 kVA PWM inverter fully controlled by a DSP controller, TMS320F241, has been used to validate the feasibility of the proposed algorithm and to demonstrate the performance of the overall system.

Análise e implementação de retificadores PWM trifásicos com resposta de tempo mínimo utilizando desacoplamento por retroação de estados

This paper develops a systematic design procedure based on discrete decoupling by state feedback applied to three-phase PWM rectifiers. A discrete model for synchronous frame is developed for three-phase PWM rectifier with an L filter. This model takes into account the computational delays presents in the discrete implementation. Deadbeat response is obtaining without the requirement of a current controller in the axis d. Moreover, discrete servo controllers to ensure unit displacement power factor and regulated DC link voltage are developed. Finally, experimental results are presented to demonstrate the feasibility of the proposed procedure, algorithms and the performance of the overall system.