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Impedance-based method is applied in this paper to analyze the relationship between the converter control system and the stability of DFIG grid connected system. The model of DFIG equivalent input admittance considering the phase error of controller system caused by PLL is proposed. The impact of controller proportional and integral gains is analyzed according to the proposed model. Stability of the...
High Voltage DC systems are gaining widespread attention due to the advances in power electronic devices and converters. MMCs are very popular nowadays in this type of application. This paper first revisits the dynamic equations of the circulating current of a MMC to incorporate a disturbance term. Based on the modified equations, a disturbance rejection controller is proposed to eliminate the double...
This paper presents a new power control strategy of grid-connected converter under grid fault conditions. Positive-and negative-sequence reactive power are controlled separately in order to effectively support unbalanced grid voltage. Both maximum phase current limit and maximum active power oscillation limit are taken into consideration which makes the converter operate safely under grid faults....
In many applications, phase shift modulation (PSM) has been proven to be a promising supplement of pulse frequency modulation (PFM) in LLC resonant converter. However, steady-state analysis of PSM LLC converter is not thoroughly studied yet. This paper presents a generalized PSM LLC model which can provide accurate prediction on resonant voltage and current behavior, dc gain and all the other steady-state...
This paper presents a real-time evaluation of power semiconductor devices in a high performance high power amplifier. The proposed method can represent the life status of the semiconductor modules in ‘odometer’ format. A special challenging case are pulsating load applications like an MRI gradient driver system. The general concepts presented have been evaluated in detail for the MRI case. A detailed...
Photovoltaic (PV) model can be a viable alternative to the conventional look-up-table as an accurate and versatile solar array simulator (SAS) engine. In PV model-based SAS, PV model has a critical role to generate appropriate I-V characteristic of the PV panel under rapidly varying temperature and irradiation, and its calculation speed as well as accuracy are key performances. In this paper, a novel...
Severe distortion will occur in the output current of inverter when grid voltage is unbalanced with harmonics contained. In this paper a scheme of repetitive control for three-phase grid-connected inverters with LCL filter under stationary frame is proposed. The THD of the injected grid current is decreased obviously with the proposed scheme. Two separate decoupled control systems can be achieved...
In this paper, a robust controller is designed to control the output voltage of an inverter with an LC type output filter in an islanded microgrid. The proposed controller includes a local droop controller, as well as a robust controller that is designed based on the μ-synthesis technique. The performance of the designed controller is proven to be robust to the uncertainties which include the time...
DC microgrid offers significant advantages such as control simplicity and less conversion stages for energy storage, renewables and electronic load integration. However, its implementation is highly restricted by the development of dc protection system. Especially, the series dc arc faults have been posing significant challenges due to low fault current level. This paper explores the impact of dc...
Due to the nonlinearity of DC-DC converters, small-signal methods do not guarantee the stability of DC-DC converters under any large-signal disturbances. In this paper, semi-tensor product of matrices with Lyapunov stability theorem is firstly adopted for analyzing the large-signal stability of DC-DC converters. A buck converter with proportional-integral (PI) controller is used as an example. Based...
It is very important for railway vehicles to have a good braking performance to avoid the phenomenon of idling and skidding, which can be implemented by looking for and keeping an optimal slip ratio. The optimal slip ratio is a value existing in the creep zone of functions between friction coefficient and slip ratio corresponding to the maximum adhesion. Controller based on the sliding mode control...
Models of converters based on averaging have been used widely with numerous benefits. Multifrequency averaging (MFA) model can predict both the fundamental and switching behavior of converters and has the faster simulation run times associated with average-value models. Third harmonic injection is commonly used in the modulation signal for three-phase inverters to increase the inverter maximum output...
This paper presents the modeling, performance analysis, and design of an undersea storage system (USS). The USS can be employed for conditioning the output power of wave energy converters (WECs) and floating wind turbines (FWTs) at sea or ocean cites. A mathematical model is developed to describe the governing equations of the USS operation. Next, based on the developed model, a storage system is...
With increasing demand for higher efficiency, engineers are looking for an alternative solution to replace induction motors (IMs) in many applications. One of the very promising topologies is the permanent magnet (PM) motor with a squirrel cage on the rotor, which is referred to as the cage rotor PM motor in this paper. Based on the literature survey, the cage rotor PM motors have been studied and...
Ultracapacitors have been widely used in urban rail vehicles as the power source because of its high power density. However, it is still a challenge to design a rapid and reliable charging control system for ultracapacitors since the DC-DC converters are highly nonlinear along with hard constraints. In this paper, the piecewise-affine (PWA) model of the ultra-capacitor charging system and a hybrid...
The battery energy stored quasi-Z-source (BES-qZS) based photovoltaic (PV) power generation system combines advantages of the qZS inverter and the battery energy storage system. However, the second harmonic (2ω) power ripple will degrade the system's performance and affect the system's design. An accurate model to analyze the 2ω ripple is very important. The existing models did not consider the battery,...
In this paper, a cooperative charging strategy is proposed for onboard supercapacitors of catenary-free trams. The multi-module charging system consists of n buck converters connected in parallel. The parallel-input parallel-output (PIPO) charging system is modeled mathematically using the averaging method. A cooperative constant-current charging control strategy is designed using the leader-follower...
In this paper, a novel reverse zero-sequence current (RZSC) compensation strategy for three-phase four-wire back-to-back active power conditioner (APC) is proposed. The objective of the APC is to achieve the active and reactive power compensation between two micro-grids. However, for the unbalanced voltage sag micro-grid system, the double-line frequency oscillation exists in the output active/reactive...
Coupled-inductor boost converters are under development for high-current, high-power applications ranging from automotive fuel cells to photovoltaics. This paper presents the small-signal analysis of a coupled-inductor boost converter operating in both CCM and DCM. Due to the complexity of operation of a coupled-inductor boost converter operating in DCM, several small-signal models must be derived...
Synchronous generators are widely utilized in microgrids with high penetration of distributed renewable energy resources for small scale power generation. An accurate model of a synchronous generator is key to effective planning and operation of a grid-tied microgrid as well as stabilizing the frequency and regulating the voltage in an islanded microgrid. In this paper, a new strategy, based on the...
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