Selective Harmonic Compensation Scheme Research Articles

Residential Distribution System Harmonic Compensation Using Priority Driven Droop Controller

As renewable energy based distributed generation (DG) units are being increasingly connected throughout today's distribution system, they can be used to mitigate harmonics caused by the wide adoption of nonlinear residential loads. To make the best use of all these DGs' ratings, it is important to develop a method to coordinate DGs' participation efforts in harmonic compensation according to their ratings and locations. Due to the low droop slope for the harmonic controller in DGs, traditional harmonic droop control methods can lead to significant harmonic sharing errors. Also, very limited work has been carried out in literature so far to identify the DGs' compensation priorities according to their locations and power rating. To address this issue, a novel priority-driven, droop-based, selective harmonic compensation scheme is developed in this work. The proposed control scheme improves the harmonic sharing accuracy. The compensation priority design and the way to integrate with droop control is studied. To ensure stability, a virtual impedance modelbased stability analysis is also discussed. Analysis, comparisons, and simulation results are used to verify the improvement of compensation performance.

Comparison between PI, PR+HC, and modified PR+HC current controller in inverter system

<span>This paper presents the comparison between proportional integral (PI) current controller, proportional resonance and harmonic compensator (PR+HC) current controller and modified PR+HC current controller in the inverter system. Power electronic components like inverter and current controller uses in the system produce unwanted harmonics that affect the quality of distribution power network. In this study, development and simulation of current controller using conventional proportional integral (PI), the selective harmonic compensation scheme (PR+HC), and modified version of the latter are considered so to overcome these harmonics injection. Modification is by adding control parameter randomisation technique to the PR+HC scheme. Results compare the three controllers and proved that with modification to the selective harmonic compensation scheme, the overall current THD can be reduced</span>

Improved Residential Distribution System Harmonic Compensation Scheme Using Power Electronics Interfaced DGs

Increased non-linear residential loads in today's distribution system is a concern due to the harmonics related power quality issues. The situation gets worsened by the harmonic resonance introduced by the installation of power factor correction (PFC) capacitor banks in the distribution network. At the same time, more and more renewable energy-based distributed generation (DG) units are being installed in the residential area. These DG systems can be used as an effective way to mitigate the harmonic related power quality problems introduced by the nonlinear residential loads. In literature, very limited work has been done to identify harmonic compensation priorities that should be assigned to different DGs operating at different locations of the distribution system for improved compensation performance. This issue is addressed in this paper. A selective harmonic compensation scheme based on modal analysis is developed to assign compensation priorities on DGs operating at different distribution system nodes for improved compensation performance. A modeled residential distribution system containing distribution components such as distribution line, PFC capacitors, transformers, and household appliances along with DG units is used to verify the improvement of compensation performance. Experimental verification of the proposed method is also provided.

Grid Harmonics Compensation Using High-Power PWM Converters Based on Combination Approach

For high-power pulsewidth modulation (PWM) converters, selective harmonic elimination (SHE) modulation scheme is commonly adopted to reduce the low-order harmonics caused by a low switching frequency. However, the SHE scheme itself lacks the capability to actively compensate the grid background harmonics. To enable the active compensation ability of the SHE-modulated PWM converters, a selective harmonic compensation scheme and an SHE phase jittering method have been proposed in the previous works, and their effectiveness to actively attenuate the one grid line current harmonic was verified on a high-power PWM current-source rectifier (CSR) system application. Nevertheless, both the two methods have difficulty in compensating two harmonics simultaneously, which limits their applications with a low resonant frequency of converter system's filter circuit. This paper extends the previous studies to enable the high-power PWM converters to actively compensate two grid background harmonics. The proposed method can not only further reduce the grid line current distortion but also make the application of the active compensation no longer limited by the filter circuit. The experimental results of its application on a high-power PWM CSR system are provided to verify the effectiveness.

Virtual Impedance-Based Selective Harmonic Compensation (VI-SHC) PWM for Current Source Rectifiers

To mitigate the line current harmonics of a high-power current source rectifier (CSR) system, the selective harmonic elimination (SHE) scheme is frequently used due to its low switching frequency and superior harmonic performance. However, the SHE scheme only focuses on the harmonics generated by the converter itself. It cannot cope with the line current harmonics caused by the background grid voltage harmonics. In this paper, a selective harmonic compensation scheme using the virtual impedance concept (VI-SHC) is presented. This method compensates for the preexisting grid background harmonics using only the line current measurement, and provides superior line current harmonic performance. The proposed method does not require measuring the grid voltage harmonics (which are typically low), does not rely on an accurate CSR system model, and therefore is very robust for practical implementation. Thi s PWM control scheme has been verified by real-time experiments on a CSR prototype.

Selective Harmonic Compensation (SHC) PWM for Grid-Interfacing High-Power Converters

Compensating the grid background harmonics in a grid-interfacing converter system, such as a drive system's active-front-end rectifier or a grid-connected inverter in a distributed generation system, is an effective method of reducing line side current harmonics. However, this harmonic compensation is particularly challenging in medium-voltage high-power applications (>1 MVA). This is mainly due to the low-switching frequency operation of high-power converters (300-800 Hz) to maintain low power loss. Therefore, the traditional tasks of active power filters with relatively high-switching frequency cannot be easily realized here. This paper proposes a new pulse width modulation technique, named selective harmonic compensation (SHC), which actively compensates the power system background harmonics, but still operates at very low-switching frequencies. Details of the proposed SHC are presented. An SHC application example on a high-power current-source rectifier is provided in this paper. The simulations and experiments show that the proposed SHC scheme can effectively compensate the system background harmonics and improve the line current harmonic performance.

A High Precision Selective Harmonic Compensation Scheme for Active Power Filters

A High Precision Selective Harmonic Compensation Scheme for Active Power Filters