Multilevel Current Source Converter Research Articles

Novel Multilevel Current Source Converter With Asymmetric Configuration: Analysis, Comparison, Modulation, and FPGA Implementation

Novel Multilevel Current Source Converter With Asymmetric Configuration: Analysis, Comparison, Modulation, and FPGA Implementation

Research on Realizing Space Vector Equivalent Modulation Output by Dual Carrier Modulation of Current Source Inverter

In order to achieve equivalent modulation of the multilevel current converter, based on the topology of three-phase multilevel current-source converters, this article presents a method to realize the output characteristic of space vector pulsewidth modulation (SVPWM) with carrier-based PWM, which can be applied in the topologies from five-level to n-level space vector modulation strategy. Different from the strategies of traditional unity theory, the proposed method analyzes the relationship directly according to the switching states of SVPWM in three-phase multilevel current-source converters. By constructing the equivalent relationship between the output level of each phase and switching states, the carriers can control the working status of the switches directly. In addition, this method is generalized to the topologies and modulation strategies under n-level, which fully reflects the correctness and universality of the proposed method. Finally, the results of simulation and experiment verify the correction of the method.

Multilevel Current Source Converter-Based STATCOM Suitable for Medium-Voltage Applications

This paper investigates the Multilevel Current Source Converter (MCSC) STATCOM. It proposes a new method of modulation. The new modulation method produces less THD and di/dt at the terminals of the MCSC STATCOM when compared to the widely used Phase-Shifted Carrier SPWM (PSC-SPWM). To ensure the inductors' currents remain balanced, a Current Balancing Algorithm (CBA) is presented. The CBA does not require any controls. It relies on assigning optimum switching states to each CSC module in real-time. In addition, two control strategies are presented in this paper. The first one assumes the STATCOM to be a SISO. Therefore, it only requires one PI controller. However, the gains for the controller must be changed if the STATCOM was to transition from capacitive mode to inductive mode, or vice versa. The second control strategy overcomes this problem by implementing a TITO integral state feedback controller. The contributions of this paper are validated via simulation and experimental results.

Research on Topology and Modulation Control Method of a Novel Three-Level Current-Fed DCDC Converter

Multilevel current source converter has the benefits of high output capacity, low current switching stress and low harmonic or ripple content. This paper presents a new topology of three-level current-fed DC/DC converter for superconducting magnetic energy storage application. In this topology, a superconducting inductance acting as a constant current source and a shunt inductance acts as current divider ensure current flows through the power switch components equally to generate immediate level of current. A novel kind of pulse width modulation (PWM) switching strategy for the current instantaneous control of the current source converter was proposed. The modulation switching strategy proposed is able to effectively control the DC current output of the converter. Also, due to the both of proposed topology and control method are quite a simple, it can be easily realized in the practice. Simulation results prove the feasibility and validity of the proposed topology and modulation strategy

Multilevel current source converters for high power medium voltage applications

In medium voltage high power applications, multi-level current source converters (CSCs) are good candidate to increase system power region, reliability, and the quality of output waveforms. Compared with widely researched voltage source multi-level converters (MLCs), the current source MLCs have the advantages of inherent short-circuit protection, high power capability and high quality of output current waveforms. The main features of MLCs include reduced harmonics, lower switching frequency and reduced current stress on each device which is a particularly important for high power application with low voltage and high current requirements. This paper conducts a general review of the current research about MLCs in higher power medium voltage application. The different types of parallel structure based MLCs and the modulation methodologies will be introduced and compared. Specifically, the circuit analysis of the common-mode (CM) loop for parallel structures will be conducted, the common-mode voltage (CMV) and circulating current suppression methods developed on the base of multilevel modulations will be addressed.

Current Source Modular Multilevel Converter: Detailed Analysis and STATCOM Application

Multilevel current source converters are a smart choice for the high-power applications with low-voltage and high-current requirements. This paper presents the detailed analysis of a current source modular multilevel converter (CSMMC) and its application as a STATCOM. Various properties of CSMMC are compared with the voltage-source modular multilevel converter (VSMMC). The submodule inductance selection method and a sorting-based algorithm for inductor current balancing are proposed for CSMMC. The validity of the inductance selection method and the inductor current balancing algorithm are confirmed by the simulation of a three-phase CSMMC using PSCAD/EMTDC. The carrier phase-shifted sinusoidal pulsewidth modulation is used as the switching technique. The performance of a converter is analyzed with interleaved and noninterleaved carrier signals for the upper and lower arms. Results show that CSMMCs and corresponding VSMMCs have analogous features. Hence, the development on VSMMCs can be used for reference to CSMMCs and vice-versa. Furthermore, the control designs for CSMMC-based STATCOM are presented and verified using simulations. The obtained results of the proposed STATCOM show that the steady-state and transient performance of the system are quite satisfactory. This makes the CSMMC suitable for HVDC and flexible ac transmission systems applications.

Simulation on Multi-Level Current Source SVG

The operational principle and topology of multi-level current source converter as well as its main advantages are introduced. According to the characteristics of SVG (Static Var Generator), a model of multi-level current source SVG is built up and simulated with PSCAD/EMTDC. The influences of model parameters on the performance of SVG are discussed in the form of dynamic and steady waveforms of system voltage and current. Simulation results display the feasibility of proposed control strategy and the excellent performance of multi-level current source SVG.

An Investigation into Thyristor-based Seven-level Multi-level Current Reinjection Current Source Converter

This article presents a comprehensive analysis of the thyristor based seven-level multi-level current reinjection current source converter. The seven-level multi-level current reinjection current source converter increases the pulse number from 12 to 72, thereby producing high-quality AC current and DC voltage waveforms, thus lowering harmonics on both sides. The ability to switch thyristors with a negative firing angle using auxiliary bridge reinjection insulated-gate bipolar transistors enables the converter to have a leading power factor. This article also details the design of the firing angle controller for the seven-level multi-level current reinjection current source converter, which enables the converter to have a negative firing angle. A wide range of PSCAD/EMTDC simulation results are presented to evaluate the performance of this converter, especially the effect of RC snubbers across the reinjection insulated-gate bipolar transistors.

Conformation of Multilevel Current Source Converter Topologies Using the Duality Principle

This paper explores the issue of constructing multilevel current source converter (MCSC) topologies using the duality principle. Three circuit cells for MCSCs are derived from the applications of the duality on the three common leg circuit cells of multilevel voltage source converters (MVSCs). Based on the presented three cells, three families of MCSC topologies, which are also corresponding to three families of MVSCs, are constructed. Analytical results show that these derived MCSCs and their corresponding MVSCs present analogous features such as the ac side currents/voltages and inductor/capacitor currents/voltages, though they are not direct dual structures. Some experimental results are given to verify the presented MCSC structures.