992 results about "Circulating current" patented technology

Secondary resonant pickup coils (102) used in loosely coupled inductive power transfer systems, with resonating capacitors (902) have high Q and could support large circulating currents which may destroy components. A current limit or "safety valve" uses an inductor designed to enter saturation at predetermined resonating currents somewhat above normal working levels. Saturation is immediate and passive. The constant-current characteristic of a loosely coupled, controlled pickup means that if the saturable section is shared by coupling flux and by leakage flux, then on saturation the current source is terminated in the saturated inductor, and little detuning from resonance occurs. Alternatively an external saturable inductor (1101, 1102) may be introduced within the resonant circuit (102 and 902), to detune the circuit away from the system frequency. Alternatively DC current may be passed through a winding to increase saturation of a saturable part of a core. As a result, a fail-safe pickup offering a voltage-limited constant-current output is provided.

A family of soft-switched, full-bridge pulse-width-modulated (FB PWM) converters provides zero-voltage-switching (ZVS) conditions for the turn-on of the bridge switches over a wide range of input voltage and output load. The FB PWM converters of this family achieve ZVS with the minimum duty cycle loss and circulating current, which optimizes the conversion efficiency. The ZVS of the primary switches is achieved by employing two magnetic components whose volt-second products change in the opposite directions with a change in phase shift between the two bridge legs. One magnetic component always operates as a transformer, where the other magnetic component can either be a coupled inductor, or uncoupled (single-winding) inductor. The transformer is used to provide isolated output(s), whereas the inductor is used to store the energy for ZVS.

Disclosed is a family of new DC/DC converters and a new control method. The converter comprises two bridge inverters, two full-wave rectification circuits and a current-doubler filter. Each inverter is able to generate a symmetrical and isolated AC output voltage. Phase-shift control is employed to control the phase difference between the two bridge inverters. By shifting the phase, the converter changes the two inverters' output voltage overlapping area to regulate its output voltage. The bridge inverters always operate at 50% duty cycle, like an open loop Bus Converter, to achieve wide-range zero voltage switching and eliminate circulating current for normal operation. For low output voltage regulation and soft start, Pulse Width Modulation (PWM) control is used. The converters and the control method improve power conversion efficiency, maximize magnetic component utilization, reduce semiconductor stress and decrease EMI emission.

The DC-DC converter connects a first and a second switching circuit for converting power mutually between direct current and alternating current respectively to a first DC power source and a second DC power source and has a transformer between the AC terminals thereof. Here, between the AC terminals of the second switching circuit and the negative pole terminal of the DC power source, a voltage clamp circuit composed of a series unit of switching devices with a reverse parallel diode and a clamp condenser is connected. An isolated bidirectional DC-DC converter which prevents a reduction in a circulating current at time of buck and an occurrence of a surge voltage at time of voltage boost and realizes highly efficiency, low noise, and miniaturization is provided.

The invention relates to an online monitoring system for high-voltage cables, which comprises a sensor, a data collection unit, a power supply device, and a network server. The sensor is arranged at the joint of a high-voltage cable and is used for collecting data such as the shield circulating current of the high-voltage cable joint, the core current, the surface temperature of the cable, and the ambient humidity and temperature and transmitting the data to the data collection unit. The data collection unit is arranged nearby the high-voltage cable joint and is used for collecting the data transmitted from the sensor and transmitting the date to the network server via a wireless network. The power supply device acquires power from the high-voltage cable and provides power to the data collection unit. The network server is installed in a control room and is used for receiving the data transmitted from the data collection unit in order to determine whether the power cable is in safe operation condition via special data analysis, thereby serving the purpose of helping maintenance personnel monitor the operation condition of the power cable at any time, and preventing the electrical faults from happening. In case that faults occur with the cable, the online monitoring system can send alarms promptly and locate fault points, thereby providing assistance for cable repair.

The embodiment of the invention provides a charging device and a mobile terminal, and belongs to the technical field of charging of batteries. The charging device comprises a charging interface, a charging circuit, a battery pack, a first switching module and a control module, wherein the battery pack comprises at least two charging batteries; the charging circuit is connected between the charging interface and the battery pack in series; the first switching module is electrically connected with the battery pack; and the control module is connected with the first switching module and controls the first switching module to switch the connection state between the charging batteries into a parallel state or a series state. The problem of heating of the batteries caused by over-high circulating currents of the batteries is solved, so that, by the charging device provided by the embodiment, the problem of heating of the batteries caused by current rise of battery bodies can be effectively solved when the batteries are quickly charged.

A soft-switched, full-bridge pulse-width-modulated (FB PWM) converter and its variations provide zero-voltage-switching (ZVS) conditions for the turn-on of the bridge switches over a wide range of input voltage and output load. The FB PWM converters of this invention achieve ZVS with a substantially reduced duty cycle loss and circulating current, which optimizes the conversion efficiency. The ZVS of the primary switches is achieved by employing an auxiliary circuit comprising an inductor and transformer to store energy for ZVS turn-on of the bridge switches.

Switching Converter with a novel two-loop Integrated magnetic structure integrates transformer and two output inductors and eliminates large circulating current in the transformer secondary side resulting in ultra high efficiency and zero ripple output current as well as zero ripple currents in both output inductors simultaneously. The novel lossless switching method eliminates the primary side switching losses to result in switching converter with highest efficiency, compact size and additional performance advantages, such as ultra low output ripple voltage, low EMI noise and improved reliability with additional benefits when operated with a front-end Power Factor Converter for computer server applications.

This present invention relates to a paralleled power conditioning system with circulating current filter, comprising: an input terminal for receiving a input power; a plurality of power conditioning units; and a load. Each power conditioning unit includes: a DC/DC converter coupled to the input for receiving the input power so as to convert the input power to a DC voltage; a DC/AC inverter coupled to the DC/DC converter for converting the DC voltage to a AC voltage; and a filter coupled to the DC/AC inverter for eliminating the noise generated by the AC voltage and the circulating current among the plurality of power conditioning units so as to generate a filter voltage. The load is connected to the plurality of power conditioning units. The plurality of power conditioning units are connected in parallel to the load.

A modular multilevel converter (MMC) circulating current suppression method is provided. The invention belongs to the technical field of electrical engineering, specifically relates to a suppression method for suppressing internal circulating current of an MMC, and solves problems of incompatibility with single phase and three phase systems, poor circulating current suppression capability and a complicated control method in conventional MMC circulating current suppression methods. According to the MMC circulating current suppression method, a wave trap is used for acquiring secondary harmonic signals in phase current; the harmonic signals in the phase current are subtracted from the average current of the phase current so that average current signals of an upper bridge arm and a lower bridge arm in which secondary harmonic waves are subtracted are acquired; the average current signals of an upper bridge arm and a lower bridge arm in which secondary harmonic waves are subtracted is taken to do subtraction with a reference current, and thus secondary harmonic signals of the circulating current is acquired; a proportional resonant controller is used for performing current tracing on the secondary harmonic waves of the circulating current, and thus voltage compensation signals are acquired; the compensation signals are processed and then are given back to sub-modules of the upper bridge arm of the MMC, and thus circulating current suppression is realized. The MMC circulating current suppression method is suitable for the technical field of electrical engineering.

The invention discloses a DC-DC converter circuit and a relevant control method; wherein, the converter comprises two DC-AC inverters; each can create symmetrical and isolated square waves or other similar AC output voltage. Through the movement of the phase of one of the DC-AC inverters, the overlapping part of the corresponding voltage of a DC output filtration circuit, which is the two DC-AC inverters can be applied to, will be changed accordingly, so as to reach the target of regulating the output voltage. A double half-bridge and double full-bridge DC-DC converters are two typical types of the converters. During normal running process, the bridge-type inverter is always running in a 50 percent of duty cycle, so as to fulfill Zero Voltage Switching (ZVS) in broad loads. Meanwhile, the invention can also eliminate circulation current, so as to improve the efficiency of power conversion. As for the adjustment and startup of low output voltage, the circuit can work in a Pulse Width Modulation (PWM) status.

The present invention relates to valve current control method based on modular multi-level converter, this method includes the control of the low frequency oscillations of the current and that of double frequency harmonic component; For said low frequency oscillations of the current, the control method includes some steps as below: first, calculate the half of the sum of the upper arm current and the lower arm current, it is the valve DC current component, said DC current component is arm circulating current; Secondly, comparing the actual value of the arm circulating current to setting value of that, the error is obtained, after some signal processing, additional output set voltage is obtained. For said the double frequency harmonic component of current, the control method includes some steps as below: firstly, figure out capacitor voltage fluctuation prediction value of the sub module; secondly, the output voltage is divided by the sum of the sub module reference voltage and the capacitor voltage fluctuation prediction value, and get the actual output set number of sub module. This method not only can realize stability of the dynamic performance of the system, but also can suppress the arm double frequency harmonic component, at the same time under the abnormal conditions of the AC system; the valve current has good output characteristics.

An apparatus and method for converting DC voltage across positive and negative DC buses to three phase AC voltages on first, second and third AC output lines, the method comprising the steps of providing first and second three phase inverters that include a first subset of inverter switches and a second subset of inverter switches, respectively, linking a first choke in series with the first three phase inverter between the positive and negative DC buses and the AC output lines, linking a second choke in series with the second three phase inverter between the positive and negative DC buses and the AC output lines and synchronously controlling the first and second inverter switch subsets so that switching of first and second inverter switch subsets is substantially synchronized among the three phases.

Proposed is a parallel inverter drive system including includes a plurality of inverter drives connected in parallel with each other, in which each inverter drive includes a switch; a PWM controller connected to the switch for controlling switching operations of the switch device according to a duty cycle signal; and a circulating current suppressor for collecting current information associated with the current of each inverter drive and a summation current, and generating an index according to the collected current information and the desired circulating current quantity. A zero-sequence voltage is generated for each phase of a three-phase voltage command according to the index and the voltage command and the operating mode of the inverter drive, thereby injecting the zero-sequence voltage into the voltage command with a feed-forward configuration so as to fix the voltage command. The PWM controller can generate the duty cycle signal according to the fixed voltage command.

Output current ripple is reduced in a three-level DC-DC power converter by connecting a plurality of phase legs in parallel between a source of input power and an output of the power converter and conducting power from the source of input power to the power converter output in an interleaved manner. The large current that results from such interleaved operation is reduced to acceptable levels, potentially less than the output current ripple of the power converter by providing inversely coupled inductors having a mutual inductance preferably greater than the inductor of the power converter in respective phase legs and in series in the circulating current path to avoid any need to increase the power converter inductance due to the circulating current. The inductor and inversely coupled inductors are preferably integrated into a single magnetic element of compact design.

Several embodiments of permanent magnet type three-phase AC rotary electric machines wherein the phase current flow is formed by parallel circuits formed by a plurality of serial circuits each comprising one or a plurality of stator coils so that electromagnetic voltage or counter electromagnetic voltage generated across opposite ends of the plural serial circuits may be always almost the same. Thus, a circulating current does not flow in the parallel circuits, whereby the efficiency of the rotary electric machine can be improved. Also, since the line current circuit of each of the phases is constituted of a parallel circuit, the current flowing in each of the stator coils is small so that the diameter of the stator coil wire can be small. Thus, the winding of the coils can be improved. Also, the processing of the coil terminals is facilitated and the processed portions of the terminals can be made small, resulting in a compact rotary electric machine.

The invention discloses a method for intelligently controlling the pressure difference of a cement raw meal vertical mill. In the method, internal pressure difference of the mill is taken as a major controlled variable, external circulating current is taken as an auxiliary controlled variable, a feeding amount is taken as a major control variable, and a water spray amount is taken as an auxiliarycontrol variable. The method comprises the following steps of: judging a current production condition according to the internal pressure difference of the mill and external circulating current information with a production rule method; and under the normal working condition, controlling the internal pressure difference of the mill by adopting GPC-PID (Generalized Predictive Control-Proportion Integration Differentiation). In the method, a mathematic model for describing the change of the pressure difference along with the feeding amount can be established only by using input and output data of a process without analyzing the complex material milling process of the raw meal vertical mill, the identifying process is simple, and online identification is available; the method has certain adaptability to the change of the production condition; and the advantages of multistep prediction, rolling optimization and feedback correction of a GPC algorithm as well as the advantages of easiness and high robustness of a PID algorithm are fully utilized, so that the labor intensity of field operating personnel is lowered greatly.

Multilevel high power converters, referred to as hexagram converters, which preferably include a combination of six three-phase converter modules, are provided herein. The three-phase converter modules are interconnected and can be configured as any three-phase converter for any given application. One or more inductors can be used in the interconnections between the six modules to suppress potential circulating currents. Numerous applications exist in which the described converters can be implemented.

The invention discloses a multi-converter parallel circulating current restraining method with quick and reactive support. For a single converter, drop control calculation is adopted, and an output reference voltage of the converter is synthesized; resistance-capacitance virtual complex impedance is guided in the output current feedback of the inverter, so that the equivalent output impedance of the converter is of resistance-capacitance performance, wherein capacity component realizes quick and reactive support of the inverter, the resonant vibration between the output impedance of the inverter and the impedance of an electrified wire fence is restricted through resistance component, and fundamental wave circulating currents and harmonic circulating currents are reduced; and through a voltage current control loop, the stability and control precision of a system are further strengthened, and accurate distribution of power is realized. According to the method, the problem that the existing method is not high in power equipartition precision, relatively large in circulating current and relatively large in voltage fluctuation, and the method can be applied to power generation parallel control systems of industrial special power supply and new power supply.