Active front-end optimization using six-pulse rectifiers in multi-motor AC drives applications

2016 IEEE Energy Conversion Congress and Exposition (ECCE)

2016

As an almost standardized configuration, Diode Rectifiers (DRs) and Silicon-Controlled Rectifiers (SCRs) are commonly employed as the front-end topology in three-phase Adjustable Speed Drive (ASD) systems. Features of this ASD configuration include: structural and control simplicity, small volume, low cost, and high reliability during operation. Yet, DRs and SCRs bring harmonic distortions in the mains and thus lowering the overall efficiency. Power quality standards/rules are thus released. For multiple ASD systems, certain harmonics of the total grid current can be mitigated by phase-shifting the currents drawn by SCR-fed drives, and thus it is much flexible to reduce the Total Harmonic Distortion (THD) level in such applications. However, the effectiveness of this harmonic mitigation scheme for multiple ASD systems depends on: a) the number of parallel drives, b) the power levels, and c) the phaseshifts (i.e., firing angles) for the corresponding SCR-fed drives. This paper thus adopts a particle swarm optimization algorithm to optimize the power levels and the firing angles for multi-drive systems considering a fixed number of drives when practically implemented. The optimization is done to minimize the THD level of the total current at the point of common coupling. Simulations with the optimized results are carried out and laboratory tests on a two-drive system are provided to demonstrate the phase-shifting harmonic mitigation scheme. Issues concerning the practical implementation of the optimal results in multi-drive systems are also addressed.

“…The phase-shifted current control method [21], [22], [26] is illustrated in the following on an n-drive system shown in Fig. 2 (n = 2).…”

Section: Phase-shifted Current Controlmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Power-quality-oriented optimization in multiple three-phase adjustable speed drives

2016 IEEE Energy Conversion Congress and Exposition (ECCE)

2016

“…To enable this phase control freedom, the DRs can be replaced by another type of rectifiers – the silicon‐controlled rectifiers (SCRs). In that case, the power quality will be enhanced by means of a phase‐shifted current control [21, 23, 24] and the boost dc‐link control/modulation. When certain phase‐shifts are introduced to parallel SCR‐drive systems, the total currents drawn from the grid will become multi‐level, and certain harmonics of interest (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…In light of the above issues, this paper proposes a harmonic mitigation strategy for SCR‐fed three‐phase parallel ASD systems in Section 2 without communication, where the basic control structure of such drives is also presented. The proposed harmonic mitigation strategy takes the strength of the phase‐shifted current control [21, 23], and then the firing angles are deliberately dispatched (e.g. linear increase) in such a way that the grid current becomes multi‐level with no communication, leading to an enhanced power quality.…”

Section: Introductionmentioning

confidence: 99%

Load‐independent harmonic mitigation in SCR‐fed three‐phase multiple adjustable speed drive systems with deliberately dispatched firing angles

2018

IET Power Electronics

Adjustable Speed Drives (ASDs) are widely used in three-phase multi-drive applications in industry for energy savings, where low-cost rectifiers (mainly Diode Rectifiers-DRs) are still employed as the front-ends in practice, also for simplicity in control and reliability in operation. However, significant harmonic distortions appear at the grid, which should be properly tackled according to increasingly stringent standards and/or grid-connection rules. If remain untreated, a poor power quality will cause efficiency drops of the entire system. Currently, communication technologies are still not of much cost-effectiveness, and hence, the use of communication in multiple parallel motordrive systems for harmonic control is rarely witnessed in industry. In this sense, this paper proposes a harmonic mitigation strategy for multiple parallel ASD systems, where another type of low-cost rectifiers (i.e., Silicon-Controlled Rectifiers-SCRs) with boost converters in the dc-link have adopted to increase the harmonic-current controllability. More specific, the SCR firing angles are deliberately dispatched among the SCR drive units, which results in certain phase shifts of the SCR currents on purpose. In such a manner, the harmonics appearing in the grid current can be mitigated to some extent in multi-drive systems without communication. The effectiveness is independent of the power loading of each drive, when a number of drives are connected. Simulations are carried out to verify the discussion. Furthermore, to make the most use of the SCR-fed structure for harmonic cancellation, a customized modulation scheme has been experimentally demonstrated. Both simulation and experiment results have verified the discussion.

“…Furthermore, in the case of multi-drive systems as demonstrated in Figs. 1 and 2, by shifting the SCR currents, the quality of the total grid current (e.g., i ga ) can be enhanced in terms of a lower THD [22], [30]- [32]. In particular, when the rectified output currents (i s and i d ) are controlled according to Fig.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Phase-Shifted Current Control for Harmonic Cancellation in Three-Phase Multiple Adjustable Speed Drive Systems

IEEE Trans. Power Delivery

2017

A phase-shifted current control can be employed to mitigate certain harmonics induced by the Diode Rectifiers (DR) and Silicon-Controlled Rectifiers (SCR) as the front-ends of multiple parallel Adjustable Speed Drive (ASD) systems. However, the effectiveness of the phase-shifted control relies on the loading condition of each drive unit as well as the number of drives in parallel. In order to enhance the harmonic cancellation by means of the phase-shifted current control, the currents drawn by the rectifiers should be maintained almost at the same level. Thus, this paper firstly analyzes the impact of unequal loading among the parallel drives, and a scheme to enhance the performance is introduced to improve the quality of the total grid current, where partial loading operation should be enabled. Simulation and experimental case studies on multidrive systems have demonstrated that the enhanced phase-shifted current control is a cost-effective solution to multiple ASD systems in terms of harmonic cancellation.