Unbalanced and Reactive Load Compensation Using MMCC-Based SATCOMs With Third-Harmonic Injection

Abstract

Abstract-Modular multilevel cascaded converter-based STATCOMs are scalable to higher voltages without requiring a step-up transformer with multiple windings and can be realised using a low switching frequency, giving lower harmonic content and hence a reduced filtering requirement. The paper presents a new injection technique to extend the operating ranges of MMCC STATCOMs when used for negative sequence and reactive current compensation. A non-sinusoidal voltage or current containing a fundamental and its third harmonic component is injected to achieve phase cluster voltage balance. This technique reduces the maximum dc-link voltage for the star configuration, and the maximum converter phase circulating current for the delta case, compared to applying only sinusoidal zero sequence components for mitigating the same degree of load unbalance. The analysis is confirmed experimentally, showing that the third harmonic injection can allow a significant improvement of STATCOM capability for simultaneous compensation of unbalanced load and reactive current.

Operation of grid‐connected DFIG using SPWM‐ and THIPWM‐based diode‐clamped multilevel inverters

“…THIPWM is a modified technique for generating modulation signals, and it has a lot of features such as reduction in the losses of commutation, greater modulation index amplitude, higher utilisation of the DC-bus voltage, and reduction in the THD of the waveform of output voltages, compared with the SPWM technique [21][22][23][24][25][26][27].…”

Comparative Study on Performance Improvement of SPWM/THIPWM based DCMLI Grid Connected DFIG

“…However, this method cannot use the full voltage of supply in the inverter and has high harmonic distortion in the produced waveform of output voltages because the SPWM characteristics of switching are not of a symmetrical nature. THIPWM is a modified technique for generating modulation signals, and it has a lot of features such as: reduction in the losses of commutation, greater modulation index amplitude, higher utilization of the DCbus voltage and reduction in the total harmonic distortion (THD) of the waveform of output voltages, compared with the SPWM technique [12][13][14][15][16][17][18].…”

Reactive Power Compensation of Modular Multilevel Cascaded Converter STATCOM using Average Power Inter-Cluster Control Method under Unbalanced Voltage Conditions

“…Several works of literature have investigated the delta-connected STATCOM [18][19][20] for grid applications. The power imbalance is the major challenge associated with MMCC-STATCOM.…”

“…This zero-sequence current component is generated through three proportional+integral controllers across the three clusters of the delta connected STATCOM. In [18] a third harmonic component of the sinusoidal zero sequence current is added to its fundamental component to extend its operating range. Authors in [13] use this sinusoidal zero sequence current in achieving intercluster balancing of STATCOM while rebalancing unbalance grid voltages.…”

“…Reactive power injection using average power balancing control with maximum current protection of MMCC based STATCOM maximum 0[18]. Comparing the maximum currents under zero-sequence current technique , 0 to the average power balancing technique…”