On control of the grid‐connected inverter (GCI) with LCL filter, the inverter‐side current model predictive control is adopted conventionally. The ultimate grid‐side current is controlled indirectly by control of inverter‐side current. The ideal scenario is that grid‐side current is directly controlled. However, the conventional control model is complicated and the calculation is heavy. This study proposed a novel direct grid‐side current model predictive control (GSC‐MPC) for GCI with LCL filter. Based on timing coordination of both forward and backward difference methods, a direct connection is established between the grid‐side output current and the inverter‐side output voltage. Meanwhile, a proper mathematical model is built for an improved model predictive control. The exact required voltage vector in the next sampling interval is predicted and calculated by this model. The output optimal voltage vector is modulated by space vector pulse width modulation technique to control the inverter. Furthermore, the proposed GSC‐MPC is rather robust to parameter variation. Simulation and experimental results present that the proposed GSC‐MPC can improve the current control performance effectively for GCI with LCL filter.

A position sensorless control of interior permanent synchronous motor (IPMSM) equipped with LC sinusoidal filter based on the full-order sliding mode observer (FOSMO) and feedforward quadrature phase-locked loop (FQPLL) is proposed in this article. The FOSMO is designed to estimate stator currents, stator voltages, and extended back electromotive forces of IPMSM. To enhance the rapidity of the convergence and accuracy of the estimation of the FOSMO, an adaptive gain matrix is designed by adopting equivalent control theory and Lyapunov stability theory. In order to suppress the dc deviation in the position estimation error under acceleration or deceleration operations, a robust and anti-interference feedforward loop without differentiator and motor parameters is added to the conventional quadrature phase-locked loop. The parameter design method of the proposed FQPLL is studied by analysis of the frequency characteristics. The experimental results verify the effectiveness of the proposed strategy.

Finite-position-set phase-locked loop (FPS-PLL) is a research hotspot in the sensorless control of permanent magnet synchronous motor (PMSM) due to its excellent dynamic response and no parameters tuning, but it takes the high computational burden and may suffer from a rotor position error of 180°. To solve the above problems, a double-cost-function FPS-PLL (DCF-FPS-PLL) is proposed in this article, where two different cost functions are defined to decide the iteration direction and guarantee the convergence of the Newton iteration method. The estimation accuracy of the rotor position is theoretically 4.73e-6 rad for the DCF-FPS-PLL without considering the error caused by the observer while only three iterations are needed, which reduces the large amount of computation without sacrificing the accuracy. The experimental results verify the advantages of the DCF-FPS-PLL.

Compared with traditional single L-type filters, LCL filters for three-phase grid-connected inverters can suppress the switching voltage and current ripple better, thus reducing harmonic pollution to the power grid. However, the increase in system order also makes it difficult to control the system. To solve the problems of complex model and severe coupling of LCL filter in the d-q coordinate system, the decoupling control of current inner loop by the linear extended state observer (LESO) was proposed based on the analysis of mathematical model of grid-connected inverter with an LCL filter. Moreover, given the relatively low speed of system response in traditional active disturbance rejection control (ADRC), the tracking differentiator (TD) was removed, and the nonlinear control law was replaced with the PI controller. Compared with the conventional feedforward decoupling method, the reasonably designed LESO used in this work can not only realize decoupling control of the original system to improve its performance, but also save the cost of sensor and achieve a better decoupling effect. The effectiveness of the proposed current control strategy was verified by experimental results.

A data-driven switching frequency control method based on finite-control-set model-predictive control (FCS-MPC) for single-phase three-level neutral-point-clamped rectifiers is proposed to achieve the accurate control of the switching frequency. Taking the switching weighting factor as input and the average switching frequency within a fixed sliding window time as output, a compact-form dynamic linearization method is used to establish an equivalent dynamic linearized data model at each dynamic operating point of the closed-loop system. Based on this data model, a data-driven controller is designed to control the switching frequency. Simulation and experimental results prove the correctness and superiority of the proposed FCS-MPC with the data-driven switching frequency control scheme.

To improve the utilization of the dc-bus voltage and solve the problem of neutral-point voltage (NP-V) unbalance and high common-mode voltage (CMV) in the overmodulation region of three-level neutral-point clamped inverters, a virtual space vector overmodulation (VSV-OVM) strategy considering NP-V balance and CMV suppression is proposed. Based on the hybrid vector correction method, the utilization of dc-bus voltage in the overmodulation region is improved, the computational burden of overmodulation algorithm is alleviated by means of fitting and establishing lookup table. Meanwhile, an effective active NP-V control method with switch states Misalignment protection is designed for the proposed VSV-OVM strategy. Furthermore, the implementation details of the proposed VSV-OVM strategy is elaborated. The experimental results verify that the proposed VSV-OVM has excellent NP-V balance and CMV suppression ability in the overmodulation region, and has higher dc-bus voltage utilization.