This paper considers the distributed event-triggered consensus problem for general linear multi-agent networks. Both the leaderless and leader-follower consensus problems are considered. Based on the local sampled state or local output information, distributed adaptive eventtriggered protocols are designed, which can ensure that consensus of the agents is achieved and the Zeno behavior is excluded by showing that the interval between any two triggering events is lower bounded by a strictly positive value. Compared to the previous related works, our main contribution is that the proposed adaptive event-based protocols are fully distributed and scalable, which do not rely on any global information of the network graph and are independent of the network's scale. In these event-based protocols, continuous communications are not required for either control laws updating or triggering functions monitoring.

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This paper investigates the distributed event-based consensus problem of switching networks satisfying the jointly connected condition. Both the state consensus of homogeneous linear networks and the output consensus of heterogeneous networks are studied. Two kinds of event-based protocols based on local sampled information are designed, without the need to solve any matrix equation or inequality. Theoretical analysis indicates that the proposed event-based protocols guarantee the achievement of consensus and the exclusion of Zeno behaviors for jointly connected undirected switching graphs. These protocols, relying on no global knowledge of the network topology and independent of switching rules, can be devised and utilized in a completely distributed manner. They are able to avoid continuous information exchanges for either controllers' updating or triggering functions' monitoring, which ensures the feasibility of the presented protocols.

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In this paper, a super-twisting algorithm (STA) second-order sliding mode control (SOSMC) is proposed for single-phase photovoltaic grid-connected voltage source inverters. The SOSMC approach is aimed to inject sinusoidal current to grid with low total harmonic distortion (THD), strong robustness to parameter variations, and fast dynamic response to solar irradiance changes. As the discontinuous sign function in the traditional sliding mode control (SMC) is replaced by the continuous super-twisting function, the chattering problem is eliminated. Furthermore, a robust sliding mode differentiator (SMD) is proposed to acquire the derivative of current reference which is difficult to obtain in practice. The stability of the system under the proposed method is proved through the Lyapunov theory. The experimental results validate that the proposed method has satisfactory performance in both dynamic and steady-state conditions, as well as disturbance rejection.INDEX TERMS Super-twisting algorithm (STA), second order sliding mode control (SOSMC), sliding mode differentiator (SMD), single-phase photovoltaic grid-connected system.

Owing to the filter resonance and background harmonics, the current control for the LCL-filtered grid-connected inverter should be carefully designed to ensure stable operation. Prior-art current control methods normally require extra sensors to achieve the damping of the resonance, or sophisticated active damping should be employed. Both increase the overall system cost and complexity. In this context, an improved control strategy is proposed for LCL-filtered inverters. The proposed control method utilizes a novel reduced-order observer in a way that only one current sensor is required for stable operation (i.e., resonance and harmonics are effectively attenuated). More specifically, the reduced-order observer embeds the dynamics of the grid voltage, where the estimated grid information is used for synchronization in a phase-locked loop. The estimated state variables of the observer are then used for the controller design. Furthermore, to achieve active damping and suppress the influence of grid voltage distortions on the current quality, a multi-resonant state-space controller is proposed, where a linear quadratic regulator method is employed to obtain the optimal gain. The simulations and experimental tests are performed on a 3-kW grid-connected inverter system with an LCL filter. The results demonstrate the effectiveness of the proposed method in terms of robust active damping and strong harmonic attenuation, and thus the inverter achieves a good power quality with only one current sensor. INDEX TERMS Active damping, linear quadratic regulator, multi-resonant controller, reduced-order observer, state-space control.

The Highly Efficient and Reliable Inverter Concept (HERIC) inverter is a cost-effective topology, which has low leakage currents and a relatively high efficiency. Thus, it is very suitable for transformerless PV systems. However, with the reported modulation methods, it is difficult to simultaneously maintain the high efficiency, good power quality, and reactive power injection of the HERIC inverter. In this paper, a hybrid unipolar pulse width modulation (UP-PWM) scheme is thus proposed to achieve those performances. The hybrid scheme adopts the conventional UP-PWM in the case of generating the positive power. When generating the negative power, a modulation scheme, which only requires the operation of freewheeling switches, is specifically proposed. Additionally, in the region of the output voltage and current zero-crossing points (ZCP), an UP-PWM with modified dead time is introduced. In order to validate the effectiveness of the proposed scheme, simulations and experiments are performed on a 4-kW HERIC inverter system with a 20-kHz switching frequency. The results demonstrate that the proposed hybrid UP-PWM method achieves a better performance in terms of reactive power injection than the conventional UP-PWM scheme, and a higher efficiency than the UP-PWM with dead time. In addition, the proposed UP-PWM scheme also enables a better power quality.