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Conventional single-vector-based direct torque control (SVB-DTC) has been widely researched owing to its simple control structure, parameter robustness and fast response. However, the SVB-DTC often features large torque and flux ripple. To suppress the large ripple in torque and stator flux, recently, a duty-cycle-based DTC (DCB-DTC) scheme applying a zero vector and a nonzero vector to the drive...
Model predictive control (MPC) has recently emerged as a powerful control method for ac motor drives, featuring quick dynamic response and intuitive concept. However, conventional MPC requires lots of calculation resources due to the enumeration of each possible voltage vector, especially in the case of a multilevel converter. To achieve good performance with low switching frequency for high power...
The paper has presented a new augmented buck converter to improve its transient performance. At first, an augmentation circuit based on diode-capacitor topology is introduced. The voltage across the inductor can be increased during load transients, and the rate of inductor current can be higher compared with conventional buck converters. Then, a hysteresis control algorithm based on output voltage...
This paper investigates the problem of accurate active power sharing in virtual flux droop where flux angle droop control is used for DG controllers instead of traditional frequency droop control. Firstly, the virtual flux droop control method is introduced. Then, the reasons for inaccurate active power sharing in flux angle droop are analysed. Further, to solve this problem, an active power compensation...
Cascaded instability problem of the cascaded power supply system is one of the most important issues that bother the researchers for a long time. In this paper, an adaptive impedance matching optimal control method for the cascaded DC-DC power supply system has been proposed to solve the cascaded instability problem. The adaptive optimal control works based on the output voltage AC signal component...
Using the conventional look-up table-direct power control (LUT-DPC) strategy with its two-level hysteresis comparators and conventional switching table, poor regulation of active power (abnormal fluctuations appeared in reactive power waveform), non-sinusoidal input currents with a little high THD and depressed power factor are obtained. This study therefore set out to solve these problems; the conventional...
This paper discloses the development of modular front-end medium-voltage solid-state transformer (SST) to show system level design, circuit topology, and prototype test results. Each multilevel front-end module consists of two stages: (1) ac to dc boost converter with power factor correction dc and (2) isolated dc-dc LLC converter. The proposed system has been designed, simulated, and fabricated with...
An innovative active-quenching circuit for single photon avalanche diode is presented. A differential amplification circuit based on offset control scheme is adopted to realize rapid avalanche signal discrimination. In order to save the die area, a voltage-controlled transistor acting as a sensing resistance is used. Compared with other traditional circuits, the proposed circuit does not need reference...
Lightning invaded over-voltage is the main cause of insulation fault of electric apparatus. To acquire the actual substation lightning invaded over-voltage, a monitoring system based on arrester valve divider is proposed in this paper. The working principle and advantages of the proposed monitoring system is analyzed firstly. And then, the actual overvoltage waveforms are presented, which are recorded...
Voltage control in the distribution system is becoming very challenging due to the enhanced number of control variables and the increasing penetration of distribution generations (e.g. photo-voltaic arrays). There is a need for new voltage control strategy considering fast control and four-quadrant operation of energy storage system in presence of the traditional voltage control devices like capacitor...
A novel positive to negative voltage converter and a novel LDO regulator are proposed in this paper. Compared with the conventional voltage converter, the proposed one has a higher efficiency for a certain process. The novel negative voltage LDO circuit has a good temperature characteristic with a simple and chip-saving control circuit. The proposed whole circuit is verified with simulation in CSMC...
Aiming at the difference between conventional power electronic interface converter and traditional synchronous generator in microgrid, it cannot provide inertial support and damping effect for microgrid. In this paper, a converter based on virtual synchronous generator technology is used to design the power outer loop and the electromagnetic equation, so that the power electronic converter has some...
The three-phase direct matrix converter has been researched exclusively as a direct AC/AC converter, being a competitive alternative to the conventional AC/DC/AC converter. Other possibilities of the matrix converter such as AC/DC, DC/AC and DC/DC conversion still remain unexplored. This paper firstly explores these possibilities and puts forward a concept of the versatile converter. With one matrix...
High voltage direct current (HVDC) transmission systems play an increasingly important role in offshore wind energy and long distance energy transmission systems. Modular multilevel converter (MMC) is an attractive topology for HVDC systems, due to its good modularity, scalability and inherent fault tolerant capabilities. For such topology, model predictive control (MPC) is a promising alternative...
This paper proposes an energy storage unit integrated dual input PV system with distributed maximum power point tracking (MPPT). Through applying a symmetrical configuration, the proposed PV system has a single stage structure to implement voltage boosting and inversion, which contributes to the advantages such as compact size and high power conversion efficiency. The design of the control strategy...
A power electronics transformer (PET) based on dual active bridge (DAB) with input series and output parallel (ISOP) cascaded topology is studied in this paper. Fe-based nanocrystalline alloys transformer cores and Silicon Carbide (SiC) power MOSFETs are adopted to improve the power density and efficiency. Mathematical derivation of the input voltage distribution is deduced with the conclusion that...
A novel space vector PWM (SVPWM) strategy is proposed in this paper to balance the neutral-point voltage (NP) and the floating capacitor voltage for five-level active neutral-point-clamped (ANPC) converter. There are two different switching sequences in each small area. According to the NP offset, different switching sequences are used to control the NP voltage. Since the charge-discharge of the floating...
In order to realize maximum power output of photovoltaics (PV), reduce line losses, and decrease abandoned solar energy during weak irradiance, a new medium voltage grid-connected PV system structure based on cascaded converters was proposed in this paper. A transformerless cascade step-up structure, instead of applying line-frequency step-up transformer, is proposed to connect PV directly to the...
This paper investigates the neutral-point (NP) potential unbalance of the fault tolerant topology of three-level neutral-point-clamped (NPC) inverter, namely the eight-switch three-phase inverter (ESTPI). It is illustrated in this paper that the conventional carrier-based pulse width modulation (CBPWM) will cause the NP potential unbalance of ESTPI. Moreover, the NP potential unbalance will lead to...
In this paper, a predictive direct power control (P-DPC) strategy for a three level NPC rectifier under ideal grid voltage is proposed, discussed and applied. With the proposed P-DPC strategy, the control targets are the active power, the reactive power and the neutral potential voltage; neither hysteresis comparators nor switching table are needed; sinusoidal input current with low total harmonic...
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