Power and Voltage Regulation of a Quad Active Bridge

The solid-state transformer (SST) has received substantial attention because of its potential in helping to achieve more intelligent grid systems. The SST is a combination of power electronic (PE) converters and a high-frequency transformer (HFT), thus, reducing volumetric footprint resulting in space savings. The SST provides several functions such as controllable voltage and disturbance isolation. It also provides a dc-link voltage that helps advancements towards complete DC distribution systems. A challenge identified from within the literature is balancing the voltages for each of the ports on the MV side of the QAB. Renewable energy supply to these ports will be stochastic in nature resulting in voltage variations at the output of the MV bridges feeding the transformer. If this is not managed appropriately, unequal power flow will be drawn by each of the ports leading to undesired voltage ripples that impact the DC-link voltage. In addition, the voltage unbalance problem makes it difficult to feed a common load without violating its voltage limits. Therefore, voltage regulation has to be investigated to target this voltage unbalance and maintain constant output voltage. The proposed approach is based upon linear–quadratic regulator (LQR) control for the DC-DC stage of the SST to alleviate the issues mentioned for improved renewable energy regulation for SST applications. Despite the effort reported, nonlinearity and uncertainty are still a challenge in some applications. So, other combined techniques have been investigated to mitigate the phenomena mentioned earlier. This motivates the use of adaptive linear–quadratic regulator (ALQR) and nonlinear model predictive control (NMPC) to track the nonlinear change of the QAB converter due to the renewable energy. Although regulation purpose has been maintained in, stability is still a challenging point in the NMPC design. Thus, a control strategy is proposed to improve the regulation of the SST based QAB considering a practical NMPC scheme with guaranteed stability

Phase Shift APOD and POD Control Technique in Multi-Level Inverters to Mitigate Total Harmonic Distortion

Multi-level inverters are widely employed to generate new energy because of their huge capacity and benefits in sound control performance. One of the critical areas of study for multi-level inverters is control strategy research. In this study, the control strategy for a multi-level inverter—which is frequently employed in HVDC and FACTS systems—is designed. An asymmetrical D.C. voltage source is supplied to create the appropriate output voltage waveform with fewer total harmonic distortions (THDs) at the output voltage and current waveforms. In this work, the pulse width modulation techniques of POD (phase opposition disposition) and APOD (alternative phase opposition disposition) MC PWM are applied to a multi-level inverter to generate the seven-level output voltage waveform. This study presents an enhanced variable carrier frequency APOD control approach that can successfully lower the overall harmonic distortion rate. The design and completion of the phase-shifting POD and APOD control strategies are followed by an analysis and comparison of the THD situation under various switching frequencies and a simulation and verification of the control strategy using MATLAB simulation. The TI DSP-based control approach has been programmed. The APOD technique increases the output voltage’s THD to 18.27%, while the output current waveform’s THD is reduced to 15.67% by utilizing the APOD PWM technique. Using the POD PWM approach increases the total harmonic distortion (THD) of the voltage waveform by 18.06% and the output current waveform’s THD by 15.45%

Enhancing fault ride-through capacity of DFIG-Based WPs by adaptive backstepping command using parametric estimation in non-linear forward power controller design

The principal issue associated with wind parks (WPs) based on doubly-fed induction generators (DFIGs) is their vulnerability to network faults. This paper presents a novel nonlinear forward power controller design with an adaptive backstepping command using parametric estimation (NFPC_ABC-PE) to enhance fault ride-through (FRT) capacities in WP utilizing DFIGs. The suggested NFPC_ABC-PE manupiles both rotor and network-side power converters (i.e., RSPCs and NSPCs). Specifically, RSPCs are manipulated to maintain the targeted voltage at dc-bus terminals, while NSPCs are manipulated to supply the reactive energy (power) necessary if the network is disturbed. As a result, the NFPC_ABC-PE proposed precisely supplies reactive energy to ensure the smooth execution of FRT ability. The method developed comprehends the dynamics of RSPC, NSPC-side filters, and dc-bus terminal voltage in the form of electrical active and reactive output power. The parameters of the RSPC and NSPC-side filters, including those associated with the dc-bus capacitor, are regarded as entirely unknown. To estimate and regulate these parameters, adaptation algorithms are utilized. The NFPC_ABC-PE employs parameter adaptation algorithms and switching control inputs designed to safeguard the overall stability of WP. The stability analysis of the DFIG-based WPs with the proposed NFPC_ABC-PE involves applying stability in the sense of the Lyapunov function (LF). To validate its efficacy, simulations are carried out on a single 10 MW power generation unit. The results of the simulation highlight a clear enhancement in the stability and FRT capability of WP, contrasting with the nonlinear forward power controller employing the sliding mode command (NFPC-SMC)