The active and reactive power controllers of grid-forming converters are traditionally designed separately, which relies on the assumption of loop decoupling. This paper proposes a full-state feedback control for the power loops of grid-forming converters. First, the power loops are modeled considering their natural coupling, which, therefore, can apply to all kinds of line impedance, i.e., resistive, inductive, or complex. Then a full-state feedback control design is used. By this way, the eigenvalues of the system can be arbitrarily placed to any positions in the timescale of power loops. Therefore, the parameters can be directly chosen by the predefined specifications. A step-by-step parameters design procedure is also given in this paper. Experimental results verify the proposed method.

Power loss estimation is an indispensable procedure to conduct lifetime prediction for power semiconductor device. The previous studies successfully perform steady-state power loss estimation for different applications, but which may be limited for the electric vehicles (EVs) with high dynamics. Based on two EV standard driving cycle profiles, this paper gives a comparative study of power loss estimation models with two different time resolutions, i.e., the output period average and the switching period average. The correspondingly estimated power losses, thermal profiles, and lifetime clearly pointed out that the widely applied power loss model with the output period average is limited for EV applications, in particular for the highly dynamic driving cycle. The difference in the predicted lifetime can be up to 300 times due to the unreasonable choice the loss model, which calls for the industry attention on the differences of the EVs and the importance of loss model selection in lifetime prediction.

The unbalance of the state-of-charges (SOCs) may be among paralleled energy storage systems (ESSs) is harmful for the system operation. This paper proposes an adaptive control strategy to achieve the balance of SOCs among the paralleled ESS-based virtual synchronous generators (VSGs) in a completely decentralized way. The parameters of the virtual governor are designed to change according to the local SOC taking the stability and steady-state frequency limitation into consideration. To realize the adaptive control, this paper starts with an analysis of the generalized requirements of the adaptive terms. Then linear relationships are chosen as an example to construct the adaptive controller. The IEEE 9-Bus system is used to verify that, with the proposed method, the SOC balancing can be gradually realized no matter the differences in the initial values and disturbances without the communication network.

The stability of frequency is at risk with increasing penetration of power electronic converters. In this case, the power grid will lack the moment of inertia to maintain a stable voltage and frequency in the event of a large disturbance. In order to improve the stability of the power grid, traditional grid-following control is needed to be transformed to grid-forming control. This paper analyzes the control structure of grid-following control and grid-forming control. Moreover, a case study is exemplified to compare the performance of two control strategies responding to frequency disturbances. Finally, a simulation model of 15 kW grid-connected converter is built in Matlab/Simulink to discuss the performance of the grid-following and grid-forming converters under different working conditions.

For the type-4 wind generation system, there is a dc link in the back-to-back converter. Whether the dc-link voltage should be controlled by the grid-side converter (GSC) or machine-side converter (MSC) is still an open question, although it is usually controlled by the GSC. Considering the stability of the system mainly depends on the GSC under weak grid conditions, two typical control methods on the GSC (i.e. power control and dc voltage control) are compared in this paper. It is found that the small-signal stability of these two control schemes are basically the same when choosing the same control loop bandwidths. Even so, the power control scheme is better than the dc voltage control scheme, because a wider range is available for tuning the power loop bandwidth to improve stability. Thus, the dc voltage control carried out on the MSC should be superior to the GSC under weak grid conditions.

Multi-sampling control provides an attractive way to reduce the control delays in LCL grid connected inverters, then the bandwidth and stability margin will be improved. However, high frequency switching harmonics (SHs) are introduced in the control loop, which may cause low frequency aliasing and deteriorate the power quality. In this paper, the multi-sampled currents are reconstructed through the double-sampled average currents, which is simple and easy to implement in a microprocessor. As a result, most of the SHs are removed and the power quality is better than the conventional multi-sampling control. Finally, a single-loop pseudo-derivative-feedback control with inverter current feedback is employed, and the effectiveness of the proposed method is verified through simulation.

Due to the increasing performance and decreasing price of microcontrollers, applying a high sampling frequency becomes more feasible in modern control. This approach is known as multisampling technology. This paper tries to give an overview of the multisampling application in power electronics converters as it enables a lot of opportunities. First, the multisampling can reduce control delays and thereby break bandwidth limitations in power electronic controllers. Secondly, a smarter control strategy can be realized with more current, voltage and system information acquired through multisampling techniques. However, this approach may also introduce two major drawbacks: risk of dead bands and high-frequency switching ripples, which may degrade the system stability margin. To address these issues, different solutions are explored and illustrated in this paper.

In order to reduce the Common-Mode Voltage (CMV) in three-to-five phase indirect matrix converters, three improved Space Vector Pulse Width Modulation (SVPWM) methods are proposed and discussed. The improved modulation schemes are achieved by reorganizing zero vectors from the inversion stage to the rectification stage. The proposed methods can not only theoretically reduce the CMV peak value by up to 47.1%, but also decrease the switching losses of the power devices. Moreover, comparisons show that a superior CMV reduction performance is achieved when only two large active voltage vectors (AVVs) in the inversion stage, which results in a large amount of third-order harmonics in output currents. In addition, the method that utilizes two adjacent active current vectors (ACVs) and the method that uses two non-adjacent ACVs in the rectification stage have the same CMV peak value. By contrast, the latter achieves a lower Total Harmonic Distortion (THD) level of the output currents. Simulation results verify the effectiveness of the proposed methods.

We present Dexmo: an inexpensive and lightweight mechanical exoskeleton system for motion capturing and force feedback in virtual reality applications. Dexmo combines multiple types of sensors, actuation units and link rod structures to provide users with a pleasant virtual reality experience. The device tracks the user's motion and uniquely provides passive force feedback. In combination with a 3D graphics rendered environment, Dexmo provides the user with a realistic sensation of interaction when a user is for example grasping an object. An initial evaluation with 20 participants demonstrate that the device is working reliably and that the addition of force feedback resulted in a significant reduction in error rate. Informal comments by the participants were overwhelmingly positive.

The control strategies of Doubly Fed Induction Generator (DFIG) system output current unbalance and distortion suppression have been well investigated in detail, with the implementation of two kinds of resonant regulators, i.e., conventional Resonance (R) regulator or Vector Proportional Integral (VPI) regulator. Nevertheless, these two resonance regulators have never been compared from the perspective of suppression capability of output current unbalance and distortion. In this paper, the impedance based analysis method is adopted to theoretically explain and compare the DFIG system impedance reshaping though the introduction of R and VPI regulator. It is pointed out that, when implemented in the DFIG system output current unbalance and distortion suppression, the VPI regulator (equivalent to the combination of virtual positive inductor and virtual positive resistor) has two advantages over R regulator (equivalent to the combination of virtual positive resistor and virtual negative inductor), i.e., better high order harmonic distortion suppression. The theoretical analysis and MATLAB simulation results have validated the correctness of this conclusion.

The Doubly-Fed Induction Generator (DFIG) based wind turbine system is presently dominant in the wind turbine market. Due to heavy load switch-off and faults in the power grid, voltage swells may occur and this phenomenon is currently given sufficient insights. This paper starts to describe the DFIG modeling and challenges when facing the symmetrical voltage swell. Then, the High Voltage Ride-Through (HVRT) capability of the DFIG can be calculated by using the demagnetizing current control, and the stator current, rotor current as well as the electromagnetic toque can be deduced during the transient voltage swell and its recovery. It is concluded that although both higher swell level and higher rotor speed cause higher rotor electromotive force, the doubly-fed induction generator can successfully ride through the grid fault due to the relatively small swell level required by the modern grid codes. Additionally, the calculated maximum stresses of the DFIG can be verified by simulation results in terms of the rotor current, stator current, and the toque at various swell levels.

In the wind power application, different asymmetrical types of the grid fault can be categorized after the Y/d transformer, and the positive and negative components of a single-phase fault, phase-to-phase fault, and two-phase fault can be summarized. Due to the newly introduced negative and even the natural component of the Doubly-Fed Induction Generator (DFIG) stator flux during the fault period, their effects on the rotor voltage can be investigated. It is concluded that the phase-to-phase fault has the worst scenario due to its highest introduction of the negative stator flux. Afterwards, the capability of a 2 MW DFIG to ride through asymmetrical grid faults can be estimated at the existing design of the power electronics converter. Finally, a control scheme aimed to improve the DFIG capability is proposed and the simulation results validate its feasibility.

In this paper, the case of symmetrical grid fault when using the multi-MW wind turbine of partial-scale and full-scale two-level power converter are designed and investigated. Firstly, the different operation behaviors of the relevant power converters under the voltage dip will be described and analyzed. Simulations of different configurations regarding the loss distribution and the junction temperature of the power device are presented in respect to the various voltage dips. It is concluded that for both systems the power loss will change dramatically during the Low-Voltage Ride Through (LVRT) condition as well as the junction temperature. For the full-scale wind turbine system, the most thermal stressed power device in the grid-side converter will appear at the grid voltage below 0.5 pu, and for the partial-scale wind turbine system, the most thermal stressed power device in the rotor-side converter will appear around 0.6 pu grid voltage.

In this paper, the multi-MW wind turbine of partial-scale and full-scale two-level power converter with DFIG and direct-drive PMSG are designed and compared in terms of their thermal performance. Simulations of different configurations regarding loss distribution and junction temperature in the power device in the whole range of wind speed are presented and analyzed. It is concluded that in both partial-scale and full-scale power converter the most thermal stressed power device in the generator-side converter will have higher mean junction temperature and larger junction temperature fluctuation compared to grid-side converter at the rated wind speed. Moreover, the thermal performance of the generator-side converter in the partial-scale power converter becomes crucial around the synchronous operating point and should be considered carefully.