632 results about "Three-phase" patented technology

The invention relates to the technical field of power generation, power transformation or power distribution, and discloses a control method for preventing overload of an energy storage system transformer, which comprises the following steps: monitoring the three-phase total power and the power of each phase of a power grid side ammeter in real time, and calculating the three-phase unbalance degree based on the three-phase total power when the three-phase unbalance phenomenon occurs; when the three-phase unbalance degree is greater than a preset unbalance degree threshold value, dynamically adjusting the charging power of the energy storage converter according to a starting threshold value, a charging limiting threshold value and a charging forbidding threshold value by adopting a multi-threshold value dynamic adjustment mechanism; the phase with the maximum deviation between the power of each phase and the average power of the three phases is calculated as an overload phase, load reduction is performed on the overload phase based on a load increasing and decreasing strategy, load increasing is performed on a non-overload phase, and the adjusted three-phase power is obtained; a power distribution instruction is calculated in real time in combination with a dynamic response mechanism, and the three-phase unbalance degree does not exceed a safety threshold value in cooperation with total power control. The problems of easy overload, three-phase imbalance and slow response of a transformer in the prior art are solved, and the purposes of accurate load control, high system stability and high response speed are achieved.

The low-power fast wake-up band-gap reference voltage circuit operates in three phases: dormant, wake-up, and steady-state phases. The circuit enters wake-up subsequent to receipt of an enable signal which causes a one-shot timer to generate a slew enable signal pulse having a predetermined period. To a band-gap voltage reference circuitry comprising an operational amplifier, there is connected, at the wake-up phase, a boost circuitry, operative under the control of the slew enable signal that connects one or more of the one or more boost circuits to a band-gap voltage reference. Thereby, during the brief wake-up phase, more current is consumed to accelerate the response of the circuit. Upon completion of the wake-up phase the boost circuitry is disconnected under the control of the slew enable signal and for as long as the enable signal is active, the circuit is operative in a low-power mode.

The invention discloses an MMC sub-module fault processing method, device and equipment and a storage medium, and the method comprises the steps: obtaining the capacitor voltage value of a sub-module of an MMC and the bridge arm current value of the sub-module, the MMC comprises six bridge arms of three phases, each bridge arm comprises a plurality of sub-modules, the capacitor of each sub-module is connected with an equivalent series resistor in series, and further, the equivalent series resistor is connected with the capacitor voltage value of the sub-module of the MMC; the resistance value of an equivalent series resistor in the sub-module is monitored through the capacitor voltage value and the bridge arm current value, if the resistance value of the equivalent series resistor is higher than a preset resistance value, it is determined that the capacitor of the sub-module fails, fault-tolerant control is carried out on the sub-module through a voltage-sharing and circulating current suppression algorithm, a three-phase switching signal is output, and the three-phase switching signal acts on the MMC. Therefore, the circulating current fundamental frequency component and the double frequency component caused by fault-tolerant control after the fault can be eliminated through the circulating current suppression strategy, the effect of circulating current suppression is achieved, and the stability of system fault operation is improved.

The invention provides a platform area power grid tail end voltage flexible regulation and control method and system. The method comprises the steps that a sampling module measures common coupling point voltage at the tail end of a platform area power grid; the impedance calculation unit obtains load end impedance; the current calculation unit calculates the current of the common coupling point through the voltage of the common coupling point and the impedance of the load end; the current resolving unit is used for resolving the common coupling point current into negative-sequence current and zero-sequence current; the compensation current unit calculates a compensation current component required for maintaining the stability of the voltage at the tail end of the transformer area power grid through the negative-sequence current and the zero-sequence current; the PWM unit generates a compensation current control signal; and the IGBT module outputs compensation current to the common coupling point. When three phases are unbalanced, the first disturbance generation circuit accurately injects a disturbance signal to effectively regulate and control the voltage at the tail end of a power grid in a transformer area; and the second disturbance generation circuit analyzes the stability of the tail end of the station area power grid by using coordinate transformation and a PI controller.

The invention provides a power fluctuation suppression method and system based on two-phase virtual phase current regulation and control. The method comprises the steps that S1, a grid-connected current model and a direct-current bus power fluctuation model are constructed; a two-phase virtual phase current regulation and control technology is introduced into the grid-connected current model; the DC bus power fluctuation model corresponds to the grid-connected current model; s2, optimizing a direct current bus power fluctuation model; and S3, solving the optimized direct current bus power fluctuation model to complete the complete suppression of the power fluctuation. On the basis of the single-phase VPCR technology, one of the phases without voltage drop in the three phases is additionally selected as an auxiliary compensation phase, optimization calculation of a two-phase virtual phase current gain coefficient is carried out through a particle swarm optimization algorithm, it is proved from the theoretical level that the two-phase VPCR technology can achieve minimization and zero of direct-current side power fluctuation, and the method is suitable for large-scale popularization and application. The traditional engineering requirements are met, and the design defect of the gain coefficient of the single-phase VPCR technology is improved.

The invention discloses a power supply circuit and electrical equipment. The power supply circuit comprises a three-phase power supply and three rectification and inversion modules, wherein each rectification and inversion module comprises a first input end, a second input end and an output end; the first input ends of the three rectification inversion modules are respectively connected to three phase lines in a three-phase power supply in a one-to-one correspondence manner; second input ends of the three rectification inversion modules are connected to a neutral line in the three-phase power supply; the output ends of the three rectification inversion modules are respectively connected to three loads in a one-to-one correspondence manner; and the rectifying and inverting module is used for sequentially rectifying and inverting the input voltage and then supplying power to corresponding loads. According to the invention, the three-phase power supply is divided into three independent single-phase power supply paths for three loads, single-phase rectification is carried out on each phase independently, the voltage level is reduced, a low-voltage-level device can be selected, and the cost is reduced; the three-phase load is balanced, the harmonic dispersion is realized, and the harmonic pollution is reduced; fault area isolation is realized, and maintenance difficulty and maintenance cost are reduced.

The invention relates to the field of voltage data processing, in particular to a voltage data processing method and device for zero point detection and a direct current brushless motor. The method comprises the following steps: respectively monitoring and acquiring voltage values of U, V and W phases; if the voltage value of one preset period is accumulated in each phase, generating a first change diagram, and calculating a first deviation value according to the generated first change diagram; translating a curve graph in the first change graph to obtain a second change graph, and calculating a second deviation value according to the second change graph; obtaining a preset number of first change diagrams corresponding to the preset periods of which accumulation is completed, and calculating a third deviation value according to the obtained first change diagrams; obtaining a fourth deviation value according to the first deviation value, the second deviation value and the third deviation value; and in the next preset period of the preset period T, correcting the latest acquired voltage values of the three phases according to the fourth deviation value to obtain corrected voltage values of the three phases. According to the invention, the problem of insufficient accuracy of voltage data is solved.

An electric machine includes a stator core defining slots having a number of radial positions. A winding is disposed in the core and has three phases, each of the phases having at least two parallel paths including hurdle-shaped conductors interconnected to form at least two continuous circuits between a terminal and a neutral. Each of the hurdle-shaped conductors have first and second uprights disposed in a different one of the slots and a bridge connecting between the uprights and extending circumferentially over an end surface of the core, wherein the bridges are stacked one on top of the other such that the winding has upper and lower layers. The bridges have variable thickness such that a number of bridges, at each of the upper and lower layers, extending over one of the slots exceeds the number of radial positions of that slot.

The invention discloses a power regulation method and device and energy storage equipment, which are applied to a transformer area, the transformer area comprises three phase lines A, B and C and at least one energy storage equipment, each energy storage equipment is respectively connected with the three phase lines, the energy storage equipment is used for regulating and controlling the voltage of the phase lines, and for each phase line connected with any energy storage equipment, the voltage of each phase line is regulated and controlled. The method comprises the steps of determining a voltage deviation value of a phase line based on a first voltage value and a reference voltage value of the phase line at a current sampling moment; obtaining a first output power and a power adjustment step length of the energy storage device at a previous sampling moment, wherein the power adjustment step length is a power adjustment value used when the first output power is generated at the previous sampling moment; and determining second output power of the energy storage equipment at the current sampling moment based on the power adjustment step length, the first output power and the voltage deviation value. The technical problem of how to adjust the energy storage system to stabilize the voltage of the transformer area when the voltage of the transformer area is in an unstable state is solved.

The invention relates to the technical field of power monitoring, in particular to a concentrator with an electrical equipment state monitoring function. Obtaining an unbalance degree according to the state characteristic values among the three phases; clustering is carried out according to the unbalance degree of all historical moments, and distribution intensity is obtained according to interval characteristics of different moments in a moment cluster; obtaining a data similarity according to the unbalance degree in the time cluster; obtaining reference credibility according to the moment quantity characteristics, the distribution intensity and the data similarity in the moment cluster; according to the difference characteristic of the unbalance degree corresponding to the current moment and the reference moment cluster and the reference credibility of the reference moment cluster, obtaining the abnormity degree; and obtaining an anomaly trend value according to the anomaly degree of the adjacent historical time period of the current moment. The early warning index of the current moment is obtained according to the abnormity degree and the abnormity trend value, and early warning is carried out, so that the monitoring accuracy of the concentrator on the power utilization state of the electrical equipment is improved.

The invention provides a braking rotating device with a power generation function, a self-powered rotating system, a control method and a wire cup, and the braking rotating device comprises a stator part which comprises three groups of coils arranged at intervals in the circumferential direction; the rotor part rotates coaxially with the stator part and comprises a plurality of magnets which are arranged at intervals in the circumferential direction and have alternately changed polarities; the self-power-generation brake part generates power based on rotation of the rotor part relative to the stator part and performs brake control on the rotor part based on a received brake signal, the self-power-generation brake part comprises a three-phase rectifier bridge circuit, and three phase current ends of the three-phase rectifier bridge circuit are respectively connected with the three groups of coils; at least one phase of the three-phase rectifier bridge circuit is provided with a switching device, at least one phase of the three-phase rectifier bridge circuit is not provided with a switching device, and when an enabling end of the switching device receives a brake signal, a phase current end of the phase where the switching device is located and a common anode or a common cathode of the three-phase rectifier bridge circuit are conducted.

The invention discloses a modular alternating support current converter without a bridge arm inductor and a modulation method thereof, and relates to the technical field of power electronics. According to the modular alternate support converter, a new modular alternate support converter topology is provided by reconstructing an operation mode of a traditional MMC, and the modular alternate support converter comprises three phase units; each phase unit comprises an upper bridge arm and a lower bridge arm which are connected in series; each bridge arm comprises N submodules which are connected in series; two ends of each phase unit serve as positive and negative poles of a direct-current end; the midpoint of the phase unit is connected with an AC filter inductor as a connecting end of three-phase power; the anode of the DC end is provided with a DC filter inductor. According to the modularized alternating supporting converter, a filter inductor does not need to be additionally arranged on a bridge arm, the modularized alternating supporting converter has the large capacity reduction amplitude and power density, the size is small, the power density is high in the corresponding alternating operation mode, the engineering implementation difficulty is low due to the full-modularized design, and good economical efficiency is achieved.

The invention relates to a single-loop control method for a static synchronous phase modifier, which belongs to the technical field of power systems, and comprises the following steps of: comparing a maximum voltage difference value in three phases with a preset voltage threshold value to obtain a voltage difference value after amplitude limiting, and obtaining a first virtual reactance by using the voltage difference value after amplitude limiting and a preset current amplitude limiting threshold value; performing proportional integral control on the difference between the maximum current value in the three phases and the current amplitude limiting threshold to obtain a second virtual reactance; virtual impedance is calculated according to the first virtual reactance and the second virtual reactance; the product of the virtual impedance and the current of each phase is used as the current amplitude limiting voltage of the corresponding phase; the modulation wave of the corresponding phase is generated by using the internal potential and the current amplitude limiting voltage of each phase, so that the voltage single-loop control and the fault current amplitude limiting of the static synchronous phase modifier are realized, the broadband oscillation risk and the overcurrent risk of the converter are effectively reduced, and the safety and the reliability of static synchronous phase modifier equipment are improved.

Common mode voltage discharge shields are disposed over end turns of stator windings for a three phase electric traction motor within an electric vehicle. The common mode voltage discharge shields are capacitively coupled to the end turns to a ground strap, providing a low impedance path for common mode voltages accumulating at a neutral for electric traction motor as a result of high frequency switching of the motor drive voltage to produce desired torque. An insulating layer separates the common mode voltage discharge shields from the end turns. Accumulation of the common mode voltage in excess of a bearing breakdown voltage, and the associated potential for discharge through bearings between the stator and rotor and electrical discharge machining, is reduced or eliminated.

The invention provides a fault identification method and system for connection of a charging pile to a low-voltage power distribution network, and relates to the technical field of electric vehicle charging, and the method comprises the steps: obtaining charging process data after the charging pile is connected to the low-voltage power distribution network, including the load of a DC charging pile and the total harmonic distortion of three phases of a power grid side; inputting the charging process data into a fault identification integrated model constructed based on an integrated bagging method to obtain a fault type; wherein the integrated bagging method is a bagging method adopting feature randomness, a sample set representing different fault scenes is generated based on a comprehensive sample set, a plurality of classifiers are trained, the trained classifiers are integrated, and a fault identification integrated model is obtained; according to the method, the feature randomness bagging method is adopted, the fault identification integrated model is constructed, the abnormal condition possibly causing the fault in the operation process of the charging pile is identified, and the fault detection accuracy is remarkably improved.

The invention provides a control method, device, circuit and equipment of a current source type converter and a medium, and belongs to the technical field of converters. The method comprises the steps of determining a maximum phase, a minimum phase and an intermediate phase based on current voltages of three phases in a three-phase alternating current; determining a first duty ratio corresponding to the maximum phase based on the current voltage of the maximum phase; determining a second duty ratio corresponding to the intermediate phase based on the current voltage of the intermediate phase; based on the second duty ratio corresponding to the intermediate phase, a third duty ratio corresponding to the minimum phase is determined, and the minimum phase and the intermediate phase complement each other; and based on the current three-phase voltage, the first duty ratio, the second duty ratio and the third duty ratio, controlling a plurality of controllable switching devices in the current source type converter to be switched on or switched off. According to the invention, the voltage stress is reduced, and the EMI performance is improved.

The embodiment of the invention provides a transformer no-load closing angle control method, electronic equipment, a storage medium and a program product. The method comprises the following steps: periodically sampling three-phase voltages at a power supply side of a transformer, and determining a zero crossing moment when the phase voltage is changed from a negative value to a positive value according to respective sampling data for each phase in the three phases; based on the zero point moment of each phase, a preset switching-on angle and the total delay required from the switching-on instruction sending to the actual conduction of the main circuit, the target moments at which the switching-on instructions of the three phases should be sent out are calculated respectively, and corresponding switching-on trigger signals are output at the target moments of the phases respectively; and in response to the closing trigger signal of each phase, combined switch circuits arranged in the three-phase line are respectively driven, and each group of combined switch circuit comprises an MOS (Metal Oxide Semiconductor) tube and a dry reed relay which are connected in parallel, so that the MOS tube is conducted to establish an initial current path.

An automatic current sharing control method for an interleaved BUCK converter belongs to the technical field of power electronics, and comprises the following steps: step S1, obtaining an output voltage and a given output voltage of a load end of the interleaved BUCK converter; obtaining the current of each phase of inductor; s2, obtaining an average value of the inductive current of each phase, and averaging the average value of the inductive current of each phase as a reference value of a current loop; s3, calculating a duty ratio signal through a current loop; s4, calculating a duty ratio signal through a voltage loop; and S5, superposing the duty ratio signal of the current loop operation of each phase with the duty ratio signal of the voltage loop operation. According to the invention, the inductive current of each phase follows the average inductive current of three phases in real time, high-precision current-sharing control is realized, and the control reliability is improved, so that the output current is controlled at an average level.

The invention provides a power converter and a detection method thereof. The power converter comprises a power conversion circuit and a control circuit. Three branches are respectively formed between three phase lines of the power conversion circuit and the N line, the three branches form a current imbalance branch, the power conversion circuit comprises an inverter circuit and a filter circuit, and the three branches are located behind the filter circuit. Under the condition that the connection of the N line is normal, the voltage of the N line is clamped by the voltage of the power grid and does not deviate from the central point, so that the difference value among the three phase voltages is smaller than the set threshold value, and when the control circuit determines that the difference value is smaller than the set threshold value, the N line is normal, and the inverter circuit can be normally started or operated. Under the condition that the N line has a fault, the current imbalance branch enables the voltage of the N line to deviate from the central point, so that the difference value among the three phase voltages is greater than the set threshold value, and when the control circuit determines that the difference value is greater than the set threshold value, the N line is considered to have abnormal connection, and an N line fault alarm signal is output.

A power storage system includes: a battery including power storages, and a switch group capable of switching a connection state of the power storages between first, second and third voltage states as defined herein; a three-phase motor in which coils of three phases are connected at a neutral point, and which is driven by electric power supplied from the battery; an inverter connected between the battery and the three-phase motor; and a DC power supply circuit connected to a first connection portion positioned between the inverter and the battery, the DC power supply circuit on a positive electrode side has a branch circuit connected to one of the coils of three phases at a second connection portion via a first semiconductor switch, and a second semiconductor switch is provided, between the second connection portion and the inverter, in one of the coils of three phases.

A power module, for power electronics of a vehicle, having two DC busbars and three phase busbars which are disposed between the two DC busbars, and a plurality of power semiconductors, each of which is disposed between one of the DC busbars and one of the phase busbars, and power electronics having at least one such power module, and a vehicle having such power electronics. The DC busbars and the phase busbars are electrically insulated from one another and in each case have at least one cooling duct through which a dielectric fluid flows, at both open ends each of the DC busbars and the phase busbars having at least one plug-in electrical contact connection and at least one plug-in fluid connection that in each case form a combined plug-in connection, so that multiple power modules are connectable to each other in fluid-tight fashion using plug connections.

A method for determining a plurality of phase labels, each phase label identifying a phase of a voltage at one of a lateral or a customer in a three phase power distribution network, comprises receiving data indicating a plurality of electrical connections of the three phase power distribution network; receiving a plurality of sensor data values, each sensor data value being a measured electrical characteristic from at least a portion of the customers; receiving a plurality of known phase labels associated with a portion of the laterals and customers; generating a form of an adjacency matrix associated with a graph of the electrical connections of the three phase power distribution network; determining the values of the adjacency matrix which minimize a mathematical function of the sensor data values and the known phase labels; and deriving the phase label for each lateral and customer from the adjacency matrix.

The invention discloses a cable dielectric loss monitoring method and system based on leakage current separation, and the method comprises the steps: collecting the grounding current and phase current of three phases of a cable, and collecting the space voltage of an intermediate phase; calculating lead angles of the grounding current and the phase current based on the grounding current, the phase current and the space voltage; in any period, separation of induced current is carried out based on the lead angles of the grounding current and the phase current at two different moments, and the phase angle of the leakage current is determined; and calculating a dielectric loss angle tangent value of each phase based on the phase angle of the leakage current. According to the method, the dielectric loss of the cable can be monitored in real time under the condition of normal operation of the cable, and the dielectric loss angle tangent value of the cable can be obtained more accurately by separating the induced current from the leakage current and calculating the phase difference between the leakage current and the space voltage, so that the aging state of the cable can be evaluated more accurately, and the service life of the cable is prolonged. And the safety and the reliability of the power system are improved.

The invention discloses a method and a system for diagnosing defects of a sheath grounding system under resonance voltage resistance of a power transmission cable. The method comprises the following steps: installing a sheath grounding current acquisition system; sequentially carrying out main insulation resonance voltage withstanding tests on three phases of the power transmission cable, and synchronously recording a grounding current waveform of a metal sheath by adopting a current acquisition system when each phase is subjected to voltage withstanding; processing the grounding current waveform by adopting a signal processing algorithm, and extracting a resonance component; and constructing a defect diagnosis matrix according to the resonance component, calculating a deviation between the defect diagnosis matrix and a standard matrix as a defect characterization value of the cable sheath grounding system, and obtaining a defect diagnosis conclusion of the sheath grounding system under the resonance withstand voltage of the power transmission cable. According to the method, the grounding current waveform of the metal sheath is synchronously acquired and analyzed in the main insulation resonance voltage withstand test of the three-phase cable, the resonance component is extracted, accurate identification of the defect is realized based on deviation calculation of the defect diagnosis matrix, and the detection sensitivity and the diagnosis reliability of the latent defect of the sheath grounding system before the cable is put into operation are improved.

In a case where three-phase coils are wound with a conductor around twelve magnetic pole teeth that are provided at equal angular intervals on an inner peripheral portion of a stator core forming a three-phase, twelve-pole stator, the winding configuration is such that the windings of the respective three phases share a first common winding pattern of the conductor around the magnetic pole teeth but differ in their circumferential positions on the stator core, and each phase winding includes a first portion and a second portion that share a second common winding pattern of the conductor around the magnetic pole teeth but differ in their circumferential positions on the stator core by half a circumference. The conductor is wound simultaneously for all of the first and second portions of the three phases by synchronously moving six nozzles feeding the conductor, relative to the stator core.

The invention provides a three-phase-in-one type parallel multi-level inverter and a motor simulator, the three-phase-in-one type parallel multi-level inverter comprises three phases of inverter circuits, each phase of inverter circuit comprises a plurality of bridge arm branches which are connected in parallel with a direct current bus power supply, the number of the bridge arm branches is equal to that of the inverter circuits, and each bridge arm branch comprises two switching devices which are connected in series; the number of the three-phase one-in-one type magnetic rings is equal to that of the bridge arm branches in any phase of inverter circuit, and each three-phase one-in-one type magnetic ring is formed by spirally winding three wires on the choking coil, one end of each of three wires of each three-phase-in-one magnetic ring is connected with the midpoint of one bridge arm branch in one phase inverter circuit, and the other end of each of the three wires forms a current output end of a corresponding phase according to an in-phase connection mode. According to the inverter provided by the invention, the cascade coupling inductor topological structure of the existing motor simulator is changed, and the problem that the high-frequency circulating current is increased along with the increase of the number of the branches is effectively solved.

The invention relates to the technical field of power system detection, in particular to a fuse wire breakage detection method and system for a single-phase isolation lightning protection device. According to the method, firstly, a complex state formed by two states is separated out, and the characteristics of the complex state are focused. The method comprises the following steps: firstly, counting abnormal moments and constructing an abnormal range, analyzing electrical characteristics in a power grid from the range, analyzing an amplitude reduction trend under each electrical dimension in the abnormal range, quantizing amplitude abnormal parameters, and comparing the amplitude abnormal parameters among three phases to obtain the abnormal amplitude of the power grid. And obtaining the disconnection probability according to the frequency change amplitude of the three-phase power supply in the abnormal range. And obtaining the overall broken line probability by using the broken line probabilities under the two electrical dimensions to judge the broken line of the fuse. According to the method, the power grid resonance state and the fuse disconnection state can be effectively distinguished through feature extraction under different electrical dimensions in a complex state and feature comparison among all items, and accurate detection of fuse disconnection is achieved.

The present application discloses an energy self-balancing flexible DC converter valve, a control method, and a DC system. The converter valve includes three phase units, each of which includes an upper bridge arm and a lower bridge arm. The upper bridge arm and the lower bridge arm are both connected in series with a number of full-bridge submodules, a number of half-bridge submodules, and bridge arm reactors. The submodules of the upper bridge arm and the lower bridge arm are both optimized MMC submodules including an energy self-balancing circuit. The energy self-balancing circuit is composed of a power electronic switch and an energy dissipation resistor in series, and is used to dissipate surplus energy when the DC transmission system has a fault that causes an overvoltage risk in the capacitor of the optimized MMC submodule. The present application can solve the technical problem of the inability to dissipate surplus power in a DC transmission system due to a fault in a new energy island ultra-long-distance DC transmission scenario at a very low cost without affecting the operating logic of the traditional converter valve. It can make full use of the capacitor of the optimized MMC submodule to temporarily store energy and reduce the heat dissipation waste of surplus power.

The invention discloses an inter-phase charge state rapid equalization method and device of a high-voltage direct-hanging energy storage system. The method comprises the steps of obtaining active and reactive components of zero-sequence current in each phase; acquiring external active and reactive current instruction values of the system in real time; judging whether a first condition is met or not; if yes, entering the second mode, otherwise, running the first mode; the first condition comprises that the absolute value of the maximum SOC deviation value among the three phases is smaller than or equal to a preset threshold value; the first mode comprises the following steps: continuously acquiring zero-sequence current regulation factors of each phase according to a preset phase current maximum threshold value, a current instruction value and active and reactive components of zero-sequence current in each phase, and selecting a real-time minimum value in the zero-sequence current regulation factors of each phase as a real-time regulation factor; multiplying the real-time regulation factor by the zero-sequence current, and injecting into the PCS; the second mode comprises the steps of multiplying the real-time regulation factor at the moment of entering the second mode by the zero-sequence current and injecting into the PCS; when the current command value changes, a first mode is entered.

Electrical apparatus (20) includes an inverter (24) having input terminals for receiving DC input power and output terminals for coupling to an AC power grid. A pulse-width modulation (PWM) generator and drivers (26) drive the switches so as to control respective amplitudes, frequencies, and phases of the output current waveforms of the inverter. Control circuitry (28) receives measurements of respective time-varying voltages and currents on the input and output terminals, computes a model (40) that includes three virtual currents flowing in a synchronous machine that is emulated by the apparatus, wherein the three virtual currents are associated respectively with the three output current waveforms, and controls the PWM generator and drivers responsively to the three virtual currents so as to synchronize the amplitudes, frequencies, and phases of the three output current waveforms of the inverter with the three phases of the AC power grid.