Abstract: Provided are hybrid passive power filter and a three-phase power system. The hybrid passive power filter includes: a series passive harmonic isolation unit, a parallel passive filtering unit, and a harmonic load; the series passive harmonic isolation unit has an input terminal electrically connected to a power grid and an output terminal electrically connected to a first terminal of the harmonic load, and the series passive harmonic isolation unit is configured to isolate harmonics; and the parallel passive filtering unit has an input terminal electrically connected to the output terminal of the series passive harmonic isolation unit and an output terminal electrically connected to a second terminal of the harmonic load, and the parallel passive filtering unit is configured to filter out harmonics.

Abstract: A method for providing grid-forming control of an inverter-based resource includes receiving, via a controller, a power reference signal. The method also includes determining a dynamic power change limit. Further, the method includes determining, via the controller, an upper power boundary and a lower power boundary for grid-induced power deviations from a desired power operating point based on the power reference signal. Moreover, the method includes determining, via the controller, limits for an inertial power regulator reference based, at least in part, on the upper and lower power boundaries and the dynamic power change limit. In addition, the method includes applying, via the controller, the limits to the inertial power regulator reference in an inertial power regulator of the inverter-based resource.

Abstract: The present invention relates to a method for operating a power plant comprising a plurality of power producing units, the power plant being operatively connected to an associated power grid having a nominal grid frequency, the method comprising the steps of determining grid frequency variations of the associated power grid, and providing, in response to the determined grid frequency variations, an active power set-point to each of the plurality of power producing units, said active power set-point causing each of the plurality of power producing units to produce active power in response to said active power set-point, said produced active power comprising, in a frequency domain, one or more active power frequency components being different from one or more undesired frequency modes. The present invention also relates to a power plant controller for performing the method.

Abstract: Aspects of the disclosure include a power system comprising at least one three-wire active harmonic filter (AHF) configured to be coupled to, and provide compensation current to, a three-phase load, at least one four-wire AHF configured to be coupled to, and provide compensation current to, the three-phase load, and a controller configured to determine a total compensation current to provide to the three-phase load, the total compensation current including a zero component and a non-zero component, determine an output capacity of the at least one three-wire AHF and the at least one four-wire AHF, calculate a current-compensation ratio based on the output capacity of the at least one three-wire AHF and the at least one four-wire AHF, and control the at least one four-wire AHF to provide at least a portion of the non-zero component of the total compensation current to the three-phase load based on the current-compensation ratio.

Abstract: A plurality of active filter devices (41, 42, 43) that each have an output connected to a harmonic-generating load device (2) and are capable of generating a compensating current for performing at least one of reduction of a harmonic current of the harmonic-generating load device (2) and improvement of the power factor of the fundamental wave are provided. The plurality of active filter devices (41, 42, 43) provide two or more types of capacities, and the number and combination of operating active filter devices among the active filter devices (41, 42, 43) change in accordance with the magnitude of the compensating current.

Abstract: A device determines a first current, of a first input phase of a power system, and a second current, of a second input phase of the power system. The device determines whether the first input phase and the second input phase are balanced based on the first current and the second current. When the first input phase and the second input phase are not balanced, the device selects the first input phase and an output phase of the power system. The device balances the first input phase and the second input phase by using the first input phase and the output phase.

Abstract: An output filter for a power train between a power supply and a motor, the filter comprising a common mode inductor, comprising an inductance for each phase line of the power train, and a resistance for each phase line, connected in parallel with the respective phase line inductance of the common mode inductor.

Abstract: A power tool includes a brushless motor including several windings, a drive circuit for driving the brushless motor, a detection device for detecting the brushless motor so as to obtain a load parameter corresponding to a load of the brushless motor, and a controller for outputting a first control signal to reduce current of the brushless motor in a first slope when the load parameter exceeds a first preset range.

Abstract: A control unit for an active filter for reducing resonance in an electric system is provided. The electric system comprises a power source distributing an alternating current to an AC conductor connected to a power consuming unit for distributing the AC to the power consuming unit. The active filter comprises a DC power source and a DC conductor connecting the DC power source to the AC conductor. The control unit comprises: a voltage measurement unit adapter to create a voltage signal on the basis of a measured voltage; a computing unit adapted to compute, using a biquadratic filter, a first compensating current on the basis of the voltage signal for reducing resonance in the electric system and a switching system placed between the DC power source and the DC conductor for creating the calculated first compensating current.

Abstract: A power flow control unit has one or more impedance injection units. The impedance injection unit has high current drivers and capacitors forming a capacitor bank, and a cooling plate. The cooling plate is thermally coupled to the high current drivers and thermally decoupled from the capacitor bank. Bus bars connect the impedance injection units in series with a power transmission line. The power flow control unit is configurable to inject into the power transmission line a reactive power of at least one MVAr (mega volt-ampere reactive).

Abstract: A positive common line and a negative common line are connected to a power source connector connected to a battery pack. First filters are provided on these two common lines, respectively. The positive common line is branched into a positive front line and a positive rear line. The negative common line is branched into a negative front line and a negative rear line. These two front lines are connected to a front power connector that is connected to a front power control unit. These two rear lines are connected to a rear power connector that is connected to a rear power control unit. It is possible to suppress electromagnetic noise on common lines.

Abstract: A harmonic current compensating device according to an embodiment of the present disclosure is a harmonic current compensating device including a power converter including at least a pair of arms each including a switching element, the harmonic current compensating device being configured to drive the switching element and supply compensating current to load current flowing between a system power source and a harmonic generating load, in which the switching element includes a unipolar device using a wide bandgap semiconductor.

Abstract: SOGI based apparatus and methods for providing balanced three phase output signals free of harmonics, DC components and imbalance present in the input signals, are disclosed. In addition, such apparatus and methods for providing corresponding output signals which are drift-free integrals of the input signals and which signals may enable the control of a power electronics inverter for improved and robust grid power injection and for motor control are disclosed.

Abstract: A harmonic trap filter suppresses at least one harmonic signal produced by an amplifier and includes an input terminal and a ground terminal. The harmonic trap filter further includes a plurality of resonators electrically coupled one to another between the input terminal and the ground terminal in a spatial order defined by relative phase shift of alternating voltage bias signals respectively applied thereto. The resonators are tuned to resonate at a frequency at which a phase delay is imparted to the at least one harmonic signal by the resonators to effect cancelation of the at least one harmonic signal at the input terminal.

Abstract: A device for suppressing harmonic distortions at the output of variable frequency drive (VFD) comprising at least one passive harmonic filter (PHF) which has a set of storage elements and a set of inductive elements. The set of inductive elements are mounted on a magnetic core. The PHF comprising at least two lines connected in parallel (parallel lines) with similar sets of elements. The described technical solution expands the possibility of operating the VFD/VSD with different supply voltage frequencies, and maintains the THD/TDD values within 5% regardless of active power fluctuations.

Abstract: A multi-line supply unit for a vehicle control unit, including at least two supply lines each connected to a vehicle voltage source at the input and brought together at a common node at the output; and a protective device, including, in each of the supply lines, at least one first damping diode looped into the supply lines in the forward direction, between the vehicle voltage source and the node; and an operating method for such a multi-line supply unit. At least one switch element is looped into each of the supply lines, respectively, in parallel with the damping diode, respectively; an evaluation and control unit measuring and evaluating a line voltage at the inputs of the supply lines, respectively, and measuring and evaluating a reverse-polarity-protected supply voltage at the common node, and controlling the switch elements in the supply lines as a function of the evaluation, using corresponding control signals.

Abstract: A printer comprising an electrical load, a control system and an electrical circuit to switchably connect the electrical load to a first phase and a second phase of a polyphase power supply. The control system monitors a first electrical current drawn by the printer on the first phase and a second electrical current drawn by the printer on the second phase. When a difference between the first electrical current and the second electrical current satisfies a threshold condition, the control system controls the electrical circuit to disconnect the electrical load from the first phase and connect the electrical load to the second phase.

Abstract: A steering system includes an electric motor drivably coupled to a steering column, and a computer communicatively coupled to the electric motor. The computer is programmed to isolate a nibble signal in data representing a torque of the steering column, and instruct the electric motor to output a motor torque based on the nibble signal shifted by a phase shift, the phase shift based on a vehicle-wheel frequency.

Abstract: Systems and methods for operating a transistor rectifier unit are provided. Aspects include providing a first transformer output and a second transformer output, providing a plurality of rectifier circuits, wherein the plurality of rectifier circuits comprises a first rectifier coupled to the first transformer output and a second rectifier coupled to the second transformer output, and wherein the first rectifier comprises a first output voltage and the second rectifier comprises a second output voltage, operating a plurality of switches based on a plurality of operational modes, wherein the plurality of operational modes comprises a first mode, a second mode, and a third mode, and wherein the plurality of switches comprises a first switch, a second switch, and a third switch.

Abstract: The present invention discloses a high-power machine drive system based on a modular multilevel converter (MMC), which belongs to the technical field of power generation, power transformation, or power distribution. The high-power machine drive system consists of a modular multilevel converter and a multi-pulse cycloconverter. The MMC outputs k phases of high-frequency AC voltages with a phase difference of 2?/k, and the multi-pulse cycloconverter outputs a low-frequency voltage to drive a corresponding machine. According to the present invention, the MMC is combined with the multi-pulse cycloconverter, and by adopting the MMC that operates at a high frequency, the capacity, the volume, and the weight of the energy storage capacitor of the MMC are reduced, the voltage level at the DC side of the MMC is increased, and the capacity of the drive system is increased.

Abstract: A power conversion device includes a three-phase voltage inverter, a two-phase/three-phase converter, a tertiary harmonic wave generator, an adder, a PWM controller, and a tertiary harmonic wave amplitude determining unit. The tertiary harmonic wave generator generates a sinusoidal tertiary harmonic wave signal synchronized with three-phase voltage command signals and having a frequency which is three times as high as that of the three-phase voltage command signal. Further, the tertiary harmonic wave generator includes a tertiary harmonic wave amplitude determining unit for determining the amplitude of the tertiary harmonic wave signal at which the power loss of a three-phase voltage inverter is minimized, based on a voltage amplitude command value responding to two-phase voltage command signals and an output power factor command value responding to an output request to a power system.

Abstract: Methods, systems, and devices for protecting a wireless power transfer system. One aspect features a sensor network for a wireless power transfer system. The sensor network includes a differential voltage sensing circuit and a current sensing circuit. The differential voltage sensing circuit is arranged within a wireless power transfer system to measure a rate of change of a voltage difference between portions of an impedance matching network and generate a first signal representing the rate of change of the voltage difference. The current sensing circuit is coupled to the differential voltage sensing circuit and configured to calculate, based on the first signal, a current through a resonator coil coupled to the wireless power transfer system.

Abstract: A method for receiving a WUR signal by an STA, according to one embodiment of the present invention, comprises the steps of: detecting a WUR preamble sequence included in a WUR PPDU through a WUR receiver of the STA, while a WLAN receiver of the STA is turned off; obtaining WUR data included in the WUR PPDU, on the basis of a timing synchronized through the WUR preamble sequence; and outputting a wake-up signal to the WLAN receiver through the WUR receiver of the STA if the WUR data is intended for the STA, wherein the WUR preamble sequence used for the synchronization corresponds to a signature sequence carrying specific information, and the specific information may include at least one of an SU/MU indicator indicating whether the WUR PPDU is for a single user (SU) or a multi-user (MU), and information on the bandwidth of the WLAN PPDU to be received after wake-up by the WLAN receiver.

Abstract: Systems and methods of the present disclosure involve passive, hybrid, and active filtering configurations to mitigate current harmonics for various electrical loads. One hybrid filtering configuration is medium voltage (MV) active filtering using a DC-DC converter and a multi-level inverter, and low voltage (LV) passive filtering. Another hybrid filtering configuration is MV passive filtering and LV active filtering using a two-level inverter. An active filtering configuration includes both MV and LV active filtering. The present disclosure also features power distribution unit (PDU) transformers electrically coupled to respective power supplies on the LV side of an electrical system. Each PDU transformer includes primary coils in a delta configuration and secondary coils in a wye configuration. The secondary coils are in series with respective leakage inductance coils. The secondary coils and the leakage inductance coils are integrated together into a single unit or module.

Abstract: The method for adjusting an inverter (1) connected to an electric motor (2) via a du/dt-filter (3) and a motor cable (4) is described. The method comprises the steps of generating a pulse on the motor cable by means of the inverter (1) measuring a cycle time of a pulse answer from consecutive current peaks, determining a time delay td from the cycle time, determining a dwell time Tdwell to be avoided from the time delay td by Tdwell=k*td, k ? {2, 6, 10, . . . } adjusting the time between consecutive switchings of the inverter (1) to be out of a range from Tdwell?tA to Tdwell+tA wherein tA is an allowable deviation from Tdwell.

Abstract: A power monitor is used to estimate the amount of input power that is supplied to a power supply. The power monitor is protected by an EMI filter within the power supply. The power monitor measures a line frequency and a line voltage within the power supply and it also retrieves empirically derived coefficient values from memory where the coefficient values are used in formulas that have been determined to model the non-linear behavior of voltage and current in the power supply. The formulas are used to estimate the discrepancy between input power to the power supply and observed power values at a power monitor. The formulas used by the power monitor calculate power compensation factors based on the measured line frequency, the measured line voltage and the retrieved formula coefficient values. The power compensation factors are used to estimate the input power supplied to the power supply.

Abstract: The present invention provides a battery management system and an electric energy storage equipped with the battery management system, which enable the adjustment of one or more variable connection voltages. In particular the energy storage of the present invention may provide highly dynamic varying output voltages, for instance in the form of an AC voltage. In this way energy storages may, for instance, be directly operated in connection with an electric power grid or may establish electric AC power grids.

Abstract: A converter arrangement includes a converter which can be switched between an AC voltage supply system and a DC voltage circuit and which has converter valves that extend between AC voltage connections and DC voltage connections. Each converter valve has a series connection of bipolar submodules that include power semiconductor devices. The converter arrangement further includes a star point reactor which is located on the AC voltage side of the converter and which has impedance coils that are interconnected to form a grounded neutral point. A suppression filter is connected between the neutral point and a ground connection. The suppression filter is configured to suppress a harmonic of an alternating voltage in the AC voltage supply system.

Abstract: A method may include operating a power system coupled to at least one information handling resource, configured to provide electrical energy to the at least one information handling resource, and comprising a plurality of voltage regulator phases, in a plurality of operational modes, each mode defining a number of the plurality of voltage regulator phases operating in a fully-enabled mode and whether or not one of the plurality of voltage regulator phases operates in a light-load mode, selecting a selected operational mode from the plurality of operational modes based on a load requirement of the at least one information handling resource, and controlling the plurality of voltage regulator phases to deliver an aggregate current in accordance with the load requirement and the selected operational mode.

Abstract: An electrical power system connected to a power grid can include a generator having a stator and a rotor and a power converter. The stator is connected to the power grid via a stator power path. The power converter can include a line-side converter coupled to the power grid via a converter power path and a rotor-side converter coupled to a rotor bus of the rotor and the line-side converter via a DC link. The rotor-side converter is configured to convert a DC power on the DC link to an AC signal for the rotor bus. The power system can also include an active filter having one or more active controlled components. The active filter is coupled in parallel with the rotor-side converter to reduce harmonics of the electrical power system.

Abstract: A circuit interruption apparatus, for an electrical network, comprising a circuit interruption device that is operatively connectable at a source side to a source of the electrical network and at a back side to a load of an electrical network. The circuit interruption device when closed permits and when open inhibits the current flow between the source side the back side. The current interruption device is configured to open when a current flowing therethrough meets or exceeds a fault current threshold. The circuit interruption apparatus also includes a fault current level determination unit that is configured to determine a predicted fault current level as a function of measured current and voltage values at the circuit interruption device before and after a variation in the current and voltage values at the circuit interruption device that result from a change of load at the back side of the circuit interruption device.

Abstract: The present invention relates to interference suppression of interference signals from an inverter. To this end, an inductor is provided at the input end of an inverter, in particular a pulse-controlled inverter. This inductor is preferably arranged between a DC voltage source and the inverter. Furthermore, two capacitors, one side of which is connected to an additional conductor, are provided between the inductor and the DC voltage source and further capacitors, one side of which is likewise connected to the additional conductor, are provided at the phase connections of the inverter.

Abstract: Embodiments of the invention provide for a system, method, and controller for operating a harmonic regulator with loop delay compensation. Some embodiments include receiving, at a controller, voltage feedback from a power system, and applying a harmonic regulator to each distortion frequency to be compensated. Embodiments also include applying a predetermined delay to an output of the harmonic regulator, scaling the delayed output and adding it to a power source voltage reference waveform, and providing condition power to a load, using the conditioned power source voltage reference waveform.

Abstract: A matrix converter system having a current control mode operation is provided. The system includes a matrix converter having a switching matrix. The matrix converter is coupled at its low-voltage side to a generator and at its output load side to a load. A controller having a pulse width modulation (PWM) control circuit is configured to control the matrix converter via its switching matrix to increase energy within the internal inductances of the generator when the switching matrix causes a short circuit. A feed forward calculator is configured to calculate a feed forward output phase angle. The feed forward output phase angle is an estimation of an angle between an output current vector and an output voltage vector that represent feedback signals of current and voltage output by the matrix converter.

Abstract: A motor drive apparatus includes a converter configured to convert AC power inputted by an AC power supply to DC power and to output the same to a DC link, a DC link capacitor provided for the DC link, an inverter configured to convert the DC power in the DC link to AC power for driving a motor and to output the AC power, a DC voltage detection unit configured to detect a value of DC voltage applied across the DC link capacitor, an AC voltage detection unit configured to detect a peak value of AC voltage on an AC input side of the converter, and a leakage current detection unit configured to detect a leakage current caused by driving the motor, based on the value of DC voltage detected by the DC voltage detection unit and the peak value of AC voltage detected by the AC voltage detection unit.

Abstract: The present invention relates to a surge suppression circuit connected between an output end of an inverter INV and a cable 100 to drive a motor M that is connected to the output end of the inverter INV via the cable 100, and relates to a motor drive system in which the surge suppression circuit is used. The surge suppression circuit 300 includes an inductance L and a resistor R connected in parallel with the inductance L. The resistor R is set so as to match, or so as to be less than, an impedance of zero-phase component of the cable 100. A surge suppression circuit and an inverter drive motor system are enabled to be applied to a low-voltage small-capacity inverter with no DC voltage neutral terminal, and enabled to reduce the zero-component of the surge voltage according to the connection to the output end of the inverter.

Abstract: Current source rectifiers (CSR) and methods for a power source including three phase lines are provided herein. The CSR includes a rectifier having a plurality of switches, each switch of the plurality of switches coupled to an associated phase line of the three phase lines. The rectifier operable to receive an alternating current (AC) input voltage and provide a direct current (DC) output voltage. The CSR also includes a controller configured to control operation of the switches in accordance with a first switching sequence when measured input voltages on at least two phase lines of the three phase lines are outside of a predetermined voltage range, and control operation of the switches in accordance with a second switching sequence when the measured input voltages on the at least two phase lines are within the predetermined voltage range.

Abstract: A control system and hardware with a controllable input relay provides two different modes of operation—uninterruptable power supply (UPS) and mixed energy-AC support. For each operation mode, regulation of the DC-Link and neutral point balancing is guaranteed even for non-linear unsymmetrical AC loads. Moreover, in the mixed energy-AC support mode, unity power factor operation of AC input source, seamless zero current crossing, and very low total harmonic distortion (THD) is provided by the applied non-linear control algorithm. The system has a higher efficiency in comparison to other AC-DC-AC converters with smaller size and weight because of the elimination of the typical balancing circuit.

Abstract: An aircraft bipolar high-voltage network includes a DC voltage converter comprising two unipolar input connections, two bipolar output connections and a reference potential connection, and at least one unipolar device having two electrical connections which are each coupled to one of the two unipolar input connections. The DC voltage converter has a first DC voltage converter module coupled to a first of the unipolar input connections via a module input connection, to the reference potential connection via a module reference potential connection and to a first of the bipolar output connections via a module output connection, and a second DC voltage converter module coupled to a second of the unipolar input connections via a module input connection, to the reference potential connection via a module reference potential connection and to a second of the bipolar output connections via a module output connection.

Abstract: The invention relates to an electric converter (30) for a substation feeding an electric grid and/or for recuperating the braking energy of rail vehicles traveling on a railroad track, the substation being connected to a feeder line able to supply a DC voltage to the rail vehicles traveling on the railroad track, the substation comprising an electricity distribution grid able to deliver a corresponding three-phase voltage with three phases, the converter (30) comprising a transformer (306) able to inspect the value of the three-phase voltage delivered by the electricity distribution grid, a filtering device (304) able to filter the three-phase voltage of the transformer (306), and an inverter (302) connected to the filter (304).

Abstract: A welding assembly and method is described which includes a charging circuit and regulator coupled to an input power source; an energy storage element connected in parallel with the charging circuit and regulator to increase the weld current output, wherein the energy storage element is charged by the charging circuit and regulator; and a weld output controller connected in parallel with the energy storage element for controlling a welding arc between an electrode and a workpiece, wherein the weld output controller includes a forward converter/inverter including a series circuit of a primary winding of a transformer, and a switching element which is coupled to the energy storage element, and a rectifier smoothing circuit which rectifies and smoothes a voltage induced in a secondary winding of the transformer according to a switching operation of the switching element, wherein the rectifier smoothing circuit conducts during an ON period of the switching element.

Abstract: An uninterruptible power supply apparatus supplies AC power from any one of a first inverter of a first power conversion device and a second inverter of a second power conversion device to a load, and when this inverter has a malfunction, the uninterruptible power supply apparatus supplies the AC power from the other inverter to the load. When a DC voltage provided to the second inverter is higher than a lower limit voltage, the second power conversion device outputs an AC voltage having a sinusoidal waveform and falling within an acceptable input voltage range of the load, and when the DC voltage is lower than the lower limit voltage, the second power conversion device outputs an AC voltage having waveform distortion within a range acceptable to the load and falling within the acceptable input voltage range of the load.

Abstract: A current regulator for a motor controller reduces distortion of the current output to a motor. Feedback signals corresponding to the current present on the motor are transformed into a fundamental and a harmonic reference frame. Notch filters in each reference frame attenuate components of the current feedback signal from the other reference frame. Current regulators in each reference frame receive the filtered current feedback signal in the corresponding reference frame and generate an output signal that is used to regulate the output current to the motor to the desired level of current in the corresponding reference frame. The output signal from the regulator in the harmonic reference frame is transformed to the fundamental reference frame, and the output of the two regulators are combined in a common reference frame to generate a reference signal corresponding to the required voltage output to the motor to achieve desired operation.

Abstract: A battery voltage measurement circuit measures voltages at a plurality of rechargeable batteries. The rechargeable batteries are connected to a flying capacitor via input-side semiconductor switches. The capacitor is connected to inverting input terminals of first and second differential amplification circuits. Output terminals of the differential amplification circuits are directly or indirectly connected to a calculation unit that calculates voltages at the rechargeable batteries. The output terminal and the inverting input terminal of each differential amplification circuit are connected via a corresponding sub-capacitor. Each differential amplification circuit includes a non-inverting input terminal connected to a reference potential. The negative electrode of the rechargeable battery is connected to the reference potential via a leakage detection circuit.

Abstract: An electric converter system including modules nested inside one another which have at least two levels of nesting is disclosed. At least one embedded module of a first nesting level is provided, which includes at least two electrical connections and a power train. The power train includes at least two embedded modules nested with each other of an at least second next lower nesting level, such that the modules are embedded inside one another. Each of the modules has switching elements for dynamically switching between switch states between at least two modules of a nesting level. A method for providing an electrical converter system is also disclosed.

Abstract: The present application is directed to a method and apparatus operable to damp reflected voltage transients in an electric motor drive system. The system includes an inverter, an electrical cable having at least one conducting cable connected to the inverter, and an electric motor connected to the electrical cable. An inner shield is disposed along a length of the at least one conducting cable. A ground line is operable for connecting the inner shield to a ground location through a resistor connected in series therewith.

Abstract: A current controller is provided having a positive sequence controller and a negative sequence controller, where error signals operated on by the positive sequence controller are transformed into a negative sequence reference frame and input to the negative sequence controller. A current controller is also provided having a positive sequence controller, a negative sequence controller, and one or more delay state feedbacks to counter control loop delays, where the delay state feedbacks provide high bandwidth, low current overshoot, small current rise time and good current stability margins. A current controller is also disclosed having a positive sequence controller, a negative sequence controller, and one or more cross coupled gains between a d-axis and a q-axis, where the cross coupled gains are proportional to the speed of a motor associated with the current controller.

Abstract: A common mode choke in a 3-wire transformer free UPS system with which different rectifier and bypass power sources are used is eliminated by using different types of PWM control depending on whether the inverter is paralleled with the bypass power source. When the inverter is paralleled with the bypass power source, a type of PWM control is used that does not have common mode voltage injection. When the inverter is not paralleled with the bypass power source, a type of PWM control is used that has common mode voltage injection. In an aspect, the PWM control that does not have common mode voltage injection is sine-triangle PWM and the PWM control that has common mode voltage injection is space-vector PWM.

Abstract: In some embodiments, the instant invention provides a drive filter that includes: a plurality of input contacts configured for receiving an initial three-phase alternative current from a three-phase alternative current power source; a plurality of output contacts configured for outputting an output current to a respective phase of an adjustable speed drive, where the adjustable speed drive has a direct current bus capacitance between 1 and 30 microfarads (uF); and a plurality of electrical connections, where each electrical connection is configured to connect each input contact of the plurality of input contacts to a respective output contact of the plurality of output contacts; and where each electrical connection consists of at least one line capacitor; and where the at least one capacitor has a capacitance value such that a total harmonic current distortion (THID) of the output current is reduced to 5 percent or less.

Abstract: The present invention provides a gradient amplifier (300) for a magnetic resonance imaging system, comprising: a power amplifier (310) configured to supply a gradient coil current to a gradient coil (330); a passive filter (320) oupled to the power amplifier and configured to damp a harmonic component of the gradient coil current, wherein an oscillation current caused by oscillation of the passive filter (320) is present in the gradient coil current; and an active power filter coupled between the passive filter and the gradient coil and configured to generate a compensation current to compensate the oscillation current.