A square wavevoltage having an amplitude equal to an output voltage of a converter is applied to an AC motor by a square wave control block. Torque control of the AC motor is performed basically by changing the voltage phase of the square wave voltage according to the torque deviation. When the motor revolution is suddenly changed, a instruction value correction unit sets a voltage instruction value of the output voltage of the converter according to a change ratio of the motor revolutions. This improves control of the motor current by changing the voltage applied to the motor in accordance with the sudden change of the motor revolutions without waiting for torque feedback control having a low control response.
A protector that protects a rectifier, and a wireless power receiver including the protector are provided. In one embodiment, a protector for an electronic device may include: a switch configured to control current flow to a rectifier of the electronic device; and a switch controller configured to: compare, with a predetermined threshold value, a voltage difference between an output voltage of the rectifier and a voltage of the electronic device; and transmit a control signal to the switch (i) to discontinue current flow to the rectifier when the voltage difference is greater than the predetermined threshold value, and (ii) to enable current flow to rectifier when the voltage difference is less than or equal to the predetermined threshold value.
A battery system includes a battery unit in which battery arms are connected in parallel, and a charge / discharge control device that controls charge / discharge of the battery unit. Each of the battery arms includes: a battery composed of one or more battery cells connected in series; a switch connected in series to the battery; and a battery monitoring device that, in a case of having detected abnormality of the battery, opens the switch to thereby isolate the battery arm including the abnormal battery, and sends a switch opening signal indicating that the switch has been opened to the charge / discharge control device. The charge / discharge control device performs a control to reduce a charge / discharge current or charge / discharge power of the battery unit when the switch opening signal is sent from the battery monitoring device of the battery unit to the charge / discharge control device.
The invention discloses an inverter protection circuit. The circuit is used for protecting a voltage source inverter in an inverter with direct current fault ride-through capability, wherein the inverter is composed of a diode valve group or a current source type valve group unit and a voltagesource type valve group unit, and the diode valve group or the current source type valve group unit and the voltagesource type valve group unit are connected in series. A bypass thyristor valve group is connected in parallel with both ends of the inverter with direct current fault ride-through capability. The anode and the cathode of the bypass thyristor valve group are connected with the positive pole and the negative pole of the inverter with direct current fault ride-through capability respectively. The invention further discloses an inverter protection method. When the voltage source inverter detects that an alternating current or direct current system is failed and the voltage or current ofthe voltage source inverter exceeds a threshold value, the bypass thyristor valve group is input, and fault information is transmitted to a rectifierstation. The rectifierstation reduces the directcurrent voltage and reduces the direct current to zero. The bypass thyristor valve group is turned off due to current zero-crossing. The voltage source inverter protection circuit effectively solvesovervoltage and overcurrent problems caused by direct current charging of the voltage source inverter, and ensures the reliable operation of the voltage source inverter.
A power supply unit, a distributed power supply system and an electric vehicle loaded therewith, capable of charge / discharge operation are disclosed. A first cell group is connected in parallel to a second cell group in which the electrolytic solution can be electrolyzed or the generated gas can be recombined. A plurality of the parallel circuit pairs are connected in series, and the series circuit is connected with a charger / discharger to constitute the power supply unit. The charger / discharger charges the power supply unit up to a voltage at which the electrolytic solution of the second cell group is electrolyzed or the generated gas is recombined.
The invention discloses a control strategy of a multi-circuit MMC (modular multilevel converter)-HVDC (high voltage direct-current ) fed extremely-weak grid. The control strategy includes that 1), a synchronous generator simulation control method is adopted to all the MMCs, an active-frequency loop is used for simulating the swinging process of a synchronous generator, an idle-voltage loop is used for simulating an excitation system of the synchronous generator, and failure current is limited and MMC response speed is increased by adopting an inner current loop; 2), a dynamic power distribution control method is adopted to power distribution among the MMCs, a preset power reference value is not used any longer, and the power reference value is dynamically adjusted according to specific proportion according to changes of system load. By the arrangement, the MMC-HVDC fed extremely-weak grid is enabled to run stably, power distribution can be rapidly and effectively performed, frequency deviation caused by power fluctuation to the system is removed, the MMCs can have inertia effect as the synchronous generator, and high reference meaning and use value in engineering are achieved.
The invention discloses a non-flux observation doubly-fed induction generatorlow voltage ride-through control method and a system, which can be applied to excitation control on a rotor-side converter of the doubly-fed induction generator in the case of deep power grid fault. The specific implementation method comprises steps: once deep fault is detected to happen to the power grid, rotor current of the doubly-fed induction generator is instantly controlled to directly track stator current at a certain ratio, and a certain compensation term related to statorvoltage is injected to a rotor current instruction for providing dynamic reactive support. The invention also provides a control systemstructure diagram for realizing the above principle. Compared with de-excitation control, flux tracking and other low voltage ride-through excitation control methods, no flux observation step is needed for generating a transient control instruction, the structure is simple, multiple control objectives such as electromagnetic torqueripple suppression or dynamic reactive power compensation can be realized, and the low voltage ride-through ability of the doubly-fed induction generator is greatly enhanced.