Model Of Voltage Source Converter Research Articles

Control strategy for hardware simplification of voltage source converter-based power applications

A hardware simplification control strategy for three-phase voltage-source-converter-based power applications is presented. The main goal of the proposal is to reduce the number of sensors needed to implement the controller while maintaining the high performance of the system. To this end, ac-voltage and dc-current sensors are replaced by software sensors based on state observers. Consequently, a more rugged, smaller and cheaper realisation can be accomplished. Regarding the voltage source converter controller, an energy function and the reactive power of the converter are considered as outputs for constructing a feedback law based on the feedback linearisation technique. In this way, internal dynamics is avoided. In order to improve controller performance, estimates of the load power and its time derivative are feedforwarded. The ac-voltages and load power estimates are obtained by designing a reduced-order non-linear observer. Several tests, with a realistic voltage source converter model that takes into account the switching power devices, validate the proposed technique. They evaluate the system performance in the presence of parameter uncertainties and disturbances in the AC input voltage.

Control and modulation methods of voltage source converter

Control and modulation methods of voltage source converterControl and modulation methods of Voltage Source Converter (VSC) have been presented in the paper. Model of VSC with three value transistor branch state function is introduced to describe operation of VSC. Predictive-corrective control method of VSC system is presented. Two variants of Space Vector PWM methods for VSC system are developed. Algorithm of cancelation of negative influence of dead time on the AC voltages is implemented in the proposed modulation methods. Correctness of introduced method is validated by simulation and experiment investigations.

Feedback Linearization Based Nonlinear Control Strategy of VSC-HVDC

The model of Voltage Source Converter (VSC) based HVDC in the synchronous dq reference frame is presented in this paper. The model includes the DC link model and the VSC models. The feedback linearization principle for Multi-input Multi-output plants is analyzed. Based on the analysis, nonlinear decoupling control strategies for the two VSCs are proposed. For one VSC, the proposed nonlinear control strategy enables it to decouple DC voltage and reactive power control, and for the other one, the strategy guarantees the control of active power and that of reactive power independently. Simulation was conducted with MATLAB/Simulink software to verify the proposed control strategies. The simulation results prove that the nonlinear decoupling control strategies are able to provide good performance.

Multivariable Dynamic Model and Robust Control of a Voltage-Source Converter for Power System Applications

This paper proposes a new multivariable dynamic model and a control approach for a voltage-source converter (VSC) based on adopting instantaneous real- and reactive-power components as the VSC dynamic variable. Using power components as the dynamic variables reduces the degree of nonlinearities of the VSC model in comparison with the conventional VSC model that uses qd current components as variables. Furthermore, since waveforms of power components are independent of the selected qd coordinates, the proposed control is more robust to the conventionally unmodelled dynamics such as dynamics of the VSC phase-locked loop system. The proposed control system regulates the VSC AC-side real- and reactive-power components, and the DC-side voltage. This paper also introduces an overcurrent limiting mechanism, based on limiting the VSC power exchange during abnormal conditions, for the proposed control system. The proposed model and control are applied to a VSC-based reactive power compensator and simulation results based on PSCAD/EMTDC software are presented.

Investigation of Subsynchronous Resonance With VSC-Based HVDC Transmission Systems

The HVDC converter control can destabilize torsional modes of nearby turbogenerators. The first experience of HVDC-turbine generator torsional interaction was observed in 1977 during field tests at Square Butte. The development of power semiconductors, specially insulated-gate bipolar transistors and gate turnoff thyristors (GTOs) has led to the small power HVDC transmission based on voltage-source converters (VSCs). The self-commutated VSC-based HVDC installations have several advantages compared to conventional HVDC-based online-commutated current source converter. The main objective of this paper is to investigate and present the detailed analysis of subsynchronous resonance (SSR), arising from a VSC-based HVDC system connected close to generating units. The analysis considers different operating modes of the converters. Based on a case study, it is shown that the dc voltage control mode of VSC operation (rectifier/inverter) close to the generator units can contribute positive damping in the torsional-mode frequency range of interest. The investigations of SSR with VSC-based HVDC is carried out based on linear (damping torque and eigenvalue) analysis and nonlinear transient simulation. While the damping torque, eigenvalue analysis, and controller design are based on the D-Q model, the transient simulation considers the D-Q model and the three-phase detailed model of VSC using switching functions. The influence of the operating modes of the converters and effects of some important parameters, such as effective short circuit ratio and generator rating are investigated.

Analysis of SSR With Three-Level Twelve-Pulse VSC-Based Interline Power-Flow Controller

The interline power-flow controller (IPFC) is a voltage-source-converter (VSC)-based flexible ac transmission system (FACTS) controller for series compensation with the unique capability of power-flow management among the multiline transmission systems of a substation. The reactive voltage injected by individual VSCs can be maintained constant or controlled to regulate active power flow in the respective line. While one VSC regulates the dc voltage, the others control the reactive power flows in the lines by injecting series active voltage. This paper presents the modelling of IPFC with 12-pulse, three-level converters and investigates the subsynchronous-resonance (SSR) characteristics of IPFC for different operating modes. The analysis of SSR is carried out based on eigenvalue analysis and transient simulation of the detailed system. It is illustrated with the help of a case study on a system adapted from the IEEE Second Benchmark Model. The analysis uses both D-Q model (neglecting harmonics in the output voltages of VSCs) and the three-phase model of VSCs using switching functions. While the eigenvalue analysis and controller design is based on the D-Q model, the transient simulation considers both models.

Real-Time Digital Hardware Simulation of Power Electronics and Drives

This paper presents a digital hardware realization of a real-time simulator for a complete induction machine drive using a field-programmable gate array (FPGA) as the computational engine. The simulator was developed using Very High Speed Integrated Circuit Hardware Description Language (VHDL), making it flexible and portable. A novel device-characteristic based model suitable for FPGA implementation has been proposed for the 2-level 6-pulse IGBT-based voltage-source converter (VSC). The VSC model is computed at a fixed time-step of 12.5 ns allowing a highly detailed and precise accounting of gating signals. The simulator also models a squirrel cage induction machine, a direct field-oriented control system, a space-vector pulse-width modulation scheme (SVPWM) and a measurement system. A multirate simulation of the system shows the slow (machine) as well as the fast (VSC and control) dynamic components. Real time simulation results under steady-state and transient conditions demonstrate modeling accuracy and efficiency

A voltage source converter model for exchanging active and reactive power with a distribution network

In this paper, some of the operational and design characteristics of a distributed superconducting magnetic energy storage (D-SMES) device are presented. The main parts that a D-SMES consists of, the various configurations and operational techniques are discussed. The advantages and disadvantages of superconducting energy storage compared with other solutions are provided. The problems that a D-SMES can deal with are listed and discussed, but in the present work we will focus only on the ability of a D-SMES to alleviate voltage fluctuations and sags (dips) and support a sensitive load during power system outages or interruptions. To demonstrate this ability of a D-SMES device, simulations were performed using the ElectroMagnetic Transients for DC (EMTDC) simulation package. The simulation results are provided and discussed.