87 results about "Three phase power system" patented technology

A power conversion device connected with a three-phase power system through a transformer, including unit converters cascade-connected so that reactors are unnecessary, and volume and weight are reduced. The secondary winding of the transformer is an open winding having six terminals. A first converter group, includes a circuit which has three converter arms, which are star-connected, connected to three of the terminals of the secondary winding. A second converter group, having three different converter arms which are star-connected, is connected to three other terminals of the secondary winding. A neutral point (the point where the star connection is made) of the first converter group, and a neutral point of the second converter group are made to be the output terminals of the power conversion device.

A robust decoder generates an output state from input signals related to the line-voltage signals of a three-phase power system, using a segment identification method based on zero-crossings derived from line-voltage difference signals. The robust decoder includes a basic decoder that provides a current output state based on the input signals, a state table that provides a presumed previous state based on the current output state of the basic decoder, a binary feed back loop including a state element for storing a previous output state, and a selector for providing the output state based on the stored previous output state and the presumed previous state. The robust decoder may be implemented as hardware or software in a digital power converter. Such a digital power converter may include boost inductors each receiving an input line voltage signal from the three-phase power system to provide phase voltage signals, switches receiving the phase voltage signals to provide an intermediate voltage signal, the plurality of switches each being control by a driving signal, an output circuit coupled to the intermediate voltage signal to provide a rectified output voltage signal for digital power converter, and a digital control circuit receiving the input line voltages and the output voltage signal, the digital control circuit generating the driving signals to control the switches. The switches may be configured according to a state machine.

A method for providing information by optimizing the data rate to a vehicle over a three-phase power line utilized to provide power to the vehicle is described. The method includes generating carrier signals in three separate frequency bands, modulating various data onto the three carrier signals to generate three transmission signals, switching the three transmission signals onto respective conductors of the three-phase power line, demodulating the various data within the vehicle, and providing the various data to one or more vehicle systems. The three transmission signals are dynamically monitored such that the three frequency bands are controlled to optimize a data rate of the transmission.

A Three-phase Power Signal Processor (TPSP) is disclosed for general three-phase power system applications. The TPSP is developed based on the concepts from adaptive filter and dynamical systems theories. The structure of the TPSP is unified as it provides a multiplicity of the signals and pieces of information without the need to change, modify, or enhance the structure or to impose excessive computational time or resource requirements. The presented TPSP receives a set of three-phase measured signals, which can be voltage, current, magnetic flux, etc, and provides (1) the instantaneous and steady-state symmetrical components, (2) the fundamental components, (3) the peak values (magnitudes) of the symmetrical components, (4) the frequency and its rate of change, (5) the synchronization signal(s) and zero-crossing instants, (6) the phase-angles of the symmetrical components, and (7) the disturbance signatures. Two or more TPSP units, when properly augmented, further provide (8) the individual harmonic components, (9) the inter-harmonics, (10) the instantaneous real and reactive current components, (11) the total harmonic distortion, dc-offset, and power factor. The TPSP can serve as the building block for various signal processing requirements encountered in the context of power system applications including power systems control, protection, monitoring, and power quality.

Provided is an apparatus and method for providing a voltage reduction for single-phase voltage regulator operation in a three-phase power system. The voltage regulator includes a plurality of tap positions selectable to adjust a voltage at a load to an in-band area. The method includes determining a measured voltage and current at the voltage regulator, determining a line voltage drop between the voltage regulator and the load if the measured voltage in the OOB area above the in-band area, and utilizing the measured voltage to lower the voltage at the load if there are no available taps. The method also includes utilizing the measured voltage less the line voltage drop to determine the tap change if there are available taps.

Disclosed is an apparatus and method for detecting a loss of a current transformer connection coupling a protective relay to a power system element of a three-phase power system and providing a plurality of secondary current waveforms of the three-phase power system to the protective relay. The apparatus includes a first logic circuit and a second logic configured to provide corresponding first and second binary signals in response to respective comparisons of calculated current value(s) of a plurality of like-phase digitized current sample streams to respective threshold values. The apparatus also includes a set reset flip-flop having a set input adapted to receive the first and second binary signals to provide a third binary signal. The third binary signal indicates loss of a current transformer connection when the set input is asserted and indicates no loss of a current transformer connection when the reset input is asserted.

Provided is an apparatus and method for providing differential protection for a phase angle regulating transformer having a load side and a source side in a three-phase power system. The method includes calculating a first positive sequence component and a first negative sequence component associated with incoming secondary currents detected on the source side, calculating a second positive sequence component and a second negative sequence component associated with outgoing secondary currents detected on the load side, applying a phase angle shift to the second positive sequence component and the second negative sequence component to form a compensated positive sequence component and a compensated negative sequence component, respectively, and determining an operate current value and a restraint current value for each of a positive and negative sequence differential element of the differential protection based on the compensated positive sequence component and the compensated negative sequence component.

Provided is an apparatus and method for providing differential protection for a phase angle regulating transformer having a load side and a source side in a three-phase power system. The method includes calculating a first positive sequence component and a first negative sequence component associated with incoming secondary currents detected on the source side, calculating a second positive sequence component and a second negative sequence component associated with outgoing secondary currents detected on the load side, applying a phase angle shift to the second positive sequence component and the second negative sequence component to form a compensated positive sequence component and a compensated negative sequence component, respectively, and determining an operate current value and a restraint current value for each of a positive and negative sequence differential element of the differential protection based on the compensated positive sequence component and the compensated negative sequence component.

Single-phase currents at two frequencies f alpha and f beta (f alpha <nxfs<f beta ) of non-integral multiples of a system fundamental wave frequency fs sandwiching an targeted harmonic (frequency nxfs) are injected between two phases of a three-phase power system as interharmonic currents. A frequency analysis of measurement current and measurement voltage of each phase in the system is carried out and a positive-phase-sequence current I1, a positive-phase-sequence voltage V1, a negative-phase-sequence current I2, and a negative-phase-sequence voltage V2 are detected for each of the two frequencies f alpha and f beta in the system based on injecting of the interharmonic currents. Positive-phase-sequence and negative-phase-sequence admittances Y1 and Y2 or positive-phase-sequence and negative-phase-sequence impedances Z1 and Z2 are found for each of the frequencies f alpha and f beta in the system as Y1=I1 / V1 and Y2=I2 / V2 or Z1=V1 / I1 and Z2=V2 / I2. Interpolation operation is performed for finding positive-phase-sequence and negative-phase-sequence admittances or positive-phase-sequence and negative-phase-sequence impedances for the targeted harmonic in the system from the admittances Y1 and Y2 or the impedances Z1 and Z2 for the frequencies f alpha and f beta .

Disclosed is an apparatus and method for detecting a loss of a current transformer connection coupling a protective relay to a power system element of a three-phase power system and providing a plurality of secondary current waveforms of the three-phase power system to the protective relay. The apparatus includes a first logic circuit and a second logic configured to provide corresponding first and second binary signals in response to respective comparisons of calculated current value(s) of a plurality of like-phase digitized current sample streams to respective threshold values. The apparatus also includes a set reset flip-flop having a set input adapted to receive the first and second binary signals to provide a third binary signal. The third binary signal indicates loss of a current transformer connection when the set input is asserted and indicates no loss of a current transformer connection when the reset input is asserted.

The invention discloses to a series connection type voltage transient variation compensation control circuit, comprising a rectification link, an inverting link and a filtration link which are sequentially connected; the circuit further comprises a by-pass switch; the control circuit adopts carrier wave inverse cascading control method; the series connection type voltage transient variation compensation control circuit and the control method in the invention have small volume and low manufacturing cost without a power frequency injection transformer and an energy storage component; the circuit can compensate transient low voltage of symmetrical three-phase power system voltage, which is only 37 percent of rated value, or can compensate transient zero voltage of one-phase to two-phase voltage, only at least one-phase voltage is rated; when the voltage is high transiently, no matter the three-phase voltage is in any case, the compensation control circuit can compensate the three-phase load voltage to be rated; in addition, the inverting link adopts a tri-level half-bridge inverting circuit to reduce voltage stress of a switch pipe when the bus bar voltage is high, and the output voltage harmonic content is reduced, so as to bring convenience to the design of a filter.

A system for determining a system charging current in a three-phase power system has a first grounding circuit that joins a neutral of the power transformer with a ground through a first resistor. System charged capacitance voltage in one phase is discharged through a second resistor in a second grounding circuit joining the one phase of the power system with the ground. A magnitude of the currents in the first and second grounding circuits are measured when the one phase is short circuited to ground. The preliminary system charging current is calculated as the root of the difference between the squares of the measured currents grounding circuits. The same procedure may be repeated for different values of the first resistor and for each of the phases, and the calculated preliminary system charging currents may be averaged to arrive at a net system charging current.

In a non-equilibrium system, estimation of the frequency, the amplitude and the phase of noncircular signals is a quite important nonlinear problem. According to the method, the original Smart DFT technology (SDFT) is extended so that the technology is enabled to be applied to real value sinusoidal signals and is also enabled to process complex value noncircular signals. The mean square error of the model can be reduced by applying the least square framework based on the linear prediction (LP) property between the continuous DFT fundamental components so that the improved complex value least square algorithm (CLS) can be obtained. Meanwhile, the invention also provides a complex value improved Pisarenko harmonic decomposition algorithm (CRPHD). The interference of noise can be removed by the method and accurate frequency estimation can be acquired, and the method can be effectively applied to the non-equilibrium three-phase power system containing the noise.

The invention discloses a software phase locking method applicable to single-phase and three-phase power systems and belongs to the technical field of grid synchronization. The design thought mainly comprises the following steps: determining a single-phase or three-phase phase-locked loop mode by virtue of a state of a control switch K, and enabling a single-phase voltage to generate two paths oforthogonal signals such as u alpha and u beta by virtue of a phase-shifting algorithm or enabling a three-phase voltage to generate the u alpha and u beta by adopting Clark coordinate transformation;enabling the u alpha and u beta to pass through a positive-sequence component extraction link and a complex band-pass filter so as to obtain a network voltage fundamental positive-sequence component;performing Park transformation to obtain u d and u q, feeding the difference of the u q and 0 into a PI controller to be regulated, adding the output quantity of the PI controller and a rated angularfrequency omega f of the power grid so as to obtain a starting phase angle by using an integrator, and obtaining the final phase angle from the starting phase angle by using a comparator and a selector. The phase locking method provided by the invention can be applicable to the single-phase and three-phase power systems, and the frequency and phase angle of the network voltage can be accurately tracked under asymmetric distorted network voltages.

A method for improving phase balance in a three-phase power system, such as a three-phase system feeding Single Wire Earth Return distribution networks. The inventive system can take power from a suitable source—including the three-phase distribution itself—and feed it to a “weaker” phase to improve balance. In addition, the system can store energy taken from the three-phase power system during off-peak periods and use this to boost a weaker phase during periods of phase imbalance. The inventive system preferably uses an organic Rankine cycle heat engine to extract stored thermal energy and use it to boost a weak phase or phases. The organic Rankine cycle heat engine may also take power from renewable sources such as solar collectors.

The invention relates to a direct current energizing method. The following steps are adopted: in a traditional direct current power supply system composed of a three-phase alternating current synchronous generator, and / or a three-phase transformer, and a three-phase rectifier, a alternating current synchronous generator of more than three phases and a rectifier which is matched with the alternating current synchronous generator in terms of a same phase number are adopted to carry out replacement and combine into an energy saving type direct current system. Through the adoption of the method of the invention, a line voltage loss of 15.8% at most in an existing three-phase power system can be reduced and even eliminated in theory, so that as for the apparatus adopting the method, the direct current voltage of the apparatus is higher than the direct current voltage of a traditional set of three-phase alternating current power generating added with the rectifier. According to the direct current energizing method, the system output power has a gain of a same degree, and the direct current power output by the rectifier is at least 10% higher than the direct current power output by the traditional rectifier. An electrical loss reduction value of the synchronous generator or the transformer is no less than 5%; therefore, the set is advantageous by being highly efficient and energy saving. An added cost proportion of the set is less than power and efficiency growing rate, and substantial technical progress and good economic benefits are achieved.

A signal analyzer for calculating the power consumption and power factor of a three-phase power system driving a motor includes logic that determines whether the analyzer's own input terminals are wired in a proper or inverted manner. To do this, the signal analyzer observes a pattern of zero crossing slope values of the three line-to-line voltages of the three-phase power system and observes a pattern of zero crossing slope values of the current in the three power lines. The analyzer also compares the slope of a voltage signal as the signal passes through zero volts and the sign of a corresponding current signal that exists as the voltage signal crosses zero volts. Based on the observed voltage and current patterns and the voltage-to-current relationships, the analyzer can positively identify which of a plurality of inputs or signal wires are inverted.

The invention relates to a method for feeding electrical current into an electrical, three-phase power supply system having a first phase, a second phase and a third phase with a first voltage, a second voltage and a third voltage at a power supply system frequency, comprising the steps of: measuring the first, second and third voltages, transforming the first, second and third voltages into a positive phase-sequence voltage system and a negative phase-sequence voltage system according to the method of symmetrical components, calculating a first desired current, a second desired current and a third desired current for feeding into the first, second and third phases of the power supply system, wherein the first, second and third desired currents are calculated on the basis of at least one value of the positive phase-sequence voltage system and / or the negative phase-sequence voltage system.

A beverage brewing apparatus having a water heating portion and a brewing portion, the water heating portion comprising a three heating element tank having three heating elements, a three phase power system, and wherein each heating element is powered by a different phase power. Each heating element may operate with a different heating capacity to better control the heating operation, controlled by a processor that manages the brewing apparatus.

The invention discloses a method for frequency estimation of a non-equilibrium three-phase power system. The method comprises the steps that the frequency of the non-equilibrium three-phase power system is estimated mainly on the basis of a widely-linear total least square self-adaption algorithm model, wherein the widely-linear model sufficiently utilizes three-phase voltage complete two-order information, and the frequency estimation robustness is enhanced. Compared with traditional linear self-adaptation estimation, the method is more applicable to the non-equilibrium system, and unbiased frequency estimation is given. Meanwhile, the model is not sensitive to changes of the three-phase voltage amplitude along with time passage and higher harmonic. The method is more stable and low in computation complexity, and the convergence performance, robust anti-noise performance and stable convergence precision are obviously improved.

A method of maintaining balance in power systems is provided herein. The method comprises of detecting a need for load switch from a source phase to a target phase; then applying a Direct Current (DC) conversion to the target phase, to yield a DC representation of the target phase; then synthesizing the DC representation of the target phase to yield synthesized source phase; then, conveying specified amount of load from the source phase to the synthesized source phase; then, repeatedly advancing, in each cycle, the phase of the synthesized source phase until it breaches the phase of target phase. The advancing is carried out in a rate of up to a standard error deviation that complies with electricity standard and conveying a load from the synthesized source phase to the target phase.

The invention relates to a method for feeding electrical current into an electrical, three-phase power supply system having a first phase, a second phase and a third phase with a first voltage, a second voltage and a third voltage at a power supply system frequency, comprising the steps of: measuring the first, second and third voltages, transforming the first, second and third voltages into a positive phase-sequence voltage system and a negative phase-sequence voltage system according to the method of symmetrical components, calculating a first desired current, a second desired current and a third desired current for feeding into the first, second and third phases of the power supply system, wherein the first, second and third desired currents are calculated on the basis of at least one value of the positive phase-sequence voltage system and / or the negative phase-sequence voltage system.

The invention is a power-electronic short-circuit trouble current limiter, composed by using a variable impedance to replace bypass inductance and transformer in the existing short-circuit trouble current limiter. As compared with existing techniques, it not only omits the bypass inductance but also need not design according to working conditions of common transformer because the variable impedance transformer allows the magnetic circuit to enter saturation as short-circuiting, number of turns, iron core section area of the variable impedance transformer, etc, can largely be reduced, the weight, bulk and cost are remarkably reduced, and simultaneously because of the saturation of the transformer iron core and the increase of leakage impedance, the inductance quantity of current limiting impedance can be reduced, making the overcurrent level remarkably reduced. The invention can implement the industrialized wide application of the shor-circuit current limiter to single-phase and three-phase power systems.

An electrical control system consisting of two or more electrical transmitting devices each capable of transmitting synchronized messages consisting of electrical pulses to devices connected to one or more of the three phases of the AC power lines in a typical three phase power system. The synchronized transmitters are each connected to neutral and to one or more of the three phases, A, B, and C, or across two of the phases, of different circuit breaker panels in a typical three phase power system, and are capable of transmitting messages to one or more of the three phases. The transmissions from the two or more transmitters are synchronized such that the transmitted pulses from each transmitter are transmitted at the same time to produce a message that can be received correctly at any receiving device connected to any of the connected circuit breaker panels.

A data communications system and associated method of data transmission for transmitting data over a three phase power system between a surface and a sub-surface location for an arrangement such as an oil field electrical submersible pump, on each of the three conductors of a three phase cabled connection with an isolation mechanism operable to isolate any given conductor when a fault associated with that conductor is detected. With the system providing a separate AC signal and data transfer on each conductor isolation can be achieved whilst enabling continued operation.

The invention discloses a phase locking method for a three-phase power system. The phase locking method includes the steps of subjecting a sampled three-phase voltage signal to lowpass filtering to acquire direct-current component in the three-phase voltage signal, subjecting the sampled three-phase voltage signal to fast Fourier transform to acquire amplitude of fundamental component in the three-phase voltage signal, subjecting the three-phase voltage signal to normalization calculation to acquire a three-phase voltage value with amplitude being 1 and not containing the direct-current component, performing DQ coordinate transformation on the three-phase voltage value and a phase position value theta outputted by a phase-locked loop to acquire component Uq of a q-axis under a rotating coordinate system, subjecting the Uq to loop filtering to acquire an angular frequency value, summing the angular frequency value and an initial angular frequency to acquire angular frequency, and performing integral operation on the angular frequency to acquire the phase position value outputted by the phase-locked loop. By the phase locking method, the phase-A fundamental wave phase position of imbalanced three-phase voltage or three-phase voltage with direct-current bias can be detected accurately and rapidly; the phase locking method is applicable to application occasions such as rectification with distorted input three-phase voltage.

The invention discloses a frequency estimation method for a three-phase power system, comprising the following steps: Step 1, acquiring three-phase voltage signals with noise of va(k), vb(k) and vc(k)in a three-phase power system, wherein k represents k time; step 2, transforming the three-phase voltage signals of va(k), vb(k) and vc(k) into a three-phase complex voltage vn(k) by the Clarke transform, and adding a three-phase voltage complex signal obtained by measuring the noise; Step 3, establishing a linear model of {vn(k), vn(k+1)} according to the three-phase voltage complex signal; Step4, using the offset compensation adaptive filtering algorithm to estimate the weight term w(k) in the linear model, obtaining a weight iteration formula after adding a deviation compensation term, and then substituting the weight iteration formula into a frequency estimation formula to obtain a frequency estimate of the three-phase power system.

According to the present invention, a fault directional detection method and device in a polyphase power system is based on harmonic analysis of currents corresponding to the sum of half-waves of the same polarity of each phase current of the power system, and each phase current (4A, 4B , 4C) comparison of changes in amplitude or any other norm value. In particular, the 2nd and 1st harmonics of the previous current are compared with the 0th harmonic respectively, and depending on the ratio, the fault can be classified as two-phase or single-phase. Comparison of the mean value (μ) of the norm of each phase (||IA||, ||IB||, ||IC||) with each said norm can further be performed with respect to the phase current sensor (12) Locate the fault.

A signal analyzer for calculating the power consumption and power factor of a three-phase power system driving a motor includes logic that determines whether the analyzer's own input terminals are wired in a proper or inverted manner. To do this, the signal analyzer observes a pattern of zero crossing slope values of the three line-to-line voltages of the three-phase power system and observes a pattern of zero crossing slope values of the current in the three power lines. The analyzer also compares the slope of a voltage signal as the signal passes through zero volts and the sign of a corresponding current signal that exists as the voltage signal crosses zero volts. Based on the observed voltage and current patterns and the voltage-to-current relationships, the analyzer can positively identify which of a plurality of inputs or signal wires are inverted.