Modulated Model Predictive Control With Branch and Band Scheme for Unbalanced Load Compensation by MMCC-STATCOM

Abstract

This paper presents a novel modulated Model-Predictive Control (MMPC) scheme for Modular Multilevel Cascaded Converter-based STATCOMs (MMCC-STATCOM) to compensate unbalanced load current and regulate reactive power flow. By adding a common mode voltage (CMV) to the phasevoltages of the star-connected MMCC current model, the method allows natural injection of a non-sinusoidal voltage to the neutral point of the converter, hence achieving inter-phase cluster voltage balance. Moreover the imposed CMV is shown to extend the operating ranges of MMCC STATCOMs when used for negative sequence current compensation. The proposed MMPC method incorporates a modified branch and bound (B&B) algorithm to optimize the per-phase switch duty ratios. It is shown to be computationally more efficient compared to model-predictive control schemes using optimal voltage level method combined with voltage sorting schemes. Experimental results with different weighting factors confirm the effectiveness of this control scheme, and compared favorably with the conventional scheme of injecting only a sinusoidal zero sequence voltage.Index Terms-Modulated model predictive control (MMPC), Branch and bound method (B&B), Multilevel modular cascaded converter-based STATCOM (MMCC-STATCOM).

Dual-Vector Model Predictive Control for Modular Multilevel Converter With Low Calculation Burden

“…Finally, based on the volt-second balance principle, a phase-shifted pulsewidth modulator (PS-PWM) is employed to generate the switching signals for each submodule to achieve fixed switching frequency. Similarly, researchers have studied methods based on volt-second balance principle combined with PS-PWM, Such as Deadbeat MPC [25], [26], MMPC [27]- [29], etc. These methods achieve a fixed switching frequency with the ability of adjusting the switching frequency.…”

DC Current Suppression in CHB-STATCOM With Model Predictive Control Employing Current Transformers

“…In the control of cascaded H-bridge STATCOMs (CHB-STATCOM), which this work is referred to, the use of a control scheme for balancing the dc-link voltage of the three phases is commonly employed [16], [17], [18]. The same approach is also used in finite control set model predictive control (FCS-MPC or direct MPC), which became a popular control technique for power converters during the last decades [19], [20], [21], [22], [23].…”

Novel DC Capacitor Voltage Balancing Strategy of Modular Multilevel Converter based STATCOM for Reactive Power Compensation and Voltage Improvement

“…Consequently, this provides an extended compensation range for the maximum load imbalance ratio, increasing it from around 58% to 65%, as demonstrated in [10]. An alternative suggestion to address the redistribution of phase active power in MMCC-STATCOM is by injecting negative sequence voltage onto the converter phase reference voltages [11]. However, this approach is primarily intended for dealing with grid voltage sag conditions.…”

“…Another variation within CCS-MPC is the optimal voltage level-based-MPC (OVL-MPC) [16]. OVL-MPC employs a cost function like the one used in [17] but evaluates the appropriate number of sub-modules to be inserted or bypassed in each phase arm based on the predicted voltages. In [18] introduced a novel approach called combined grouping and sorting optimal MPC for MMC HVDC.…”