Abstract: Transformer assembly including a first transformer stage having a plurality of first-stage transformer cells; and a second transformer stage. An input of the second transformer stage is connected to an output of the first transformer stage. A lightning impulse breakdown voltage of a transformer cell of the second stage is at least double of a lightning impulse breakdown voltage of transformer cells of the first stage.

Abstract: To enable overmodulation control having high controllability and low noise characteristics, a control device of an AC motor includes an inverter for driving an AC motor and a controller for controlling the inverter by pulse width modulation. The controller, when over-modulating the inverter, limits the amplitude of the voltage command in the pulse width modulation to a predetermined upper limit value or less.

Abstract: A power supply system comprises: a switched-capacitor converter, a transformer, and a voltage converter. The switched-capacitor converter includes multiple capacitors. The multiple capacitors are controllably switched in a circuit path including a primary winding of the transformer to convert the first voltage into a second voltage. The voltage converter converts the first voltage produced by the switched-capacitor converter into the second voltage that powers a load.

Abstract: Current control section 2 performs PI control based on deviation between d-axis command current Id_cmd and d-axis detected current Id_det and deviation between q-axis command current Iq_cmd and q-axis detected current Iq_det. Neutral point potential control section 4 calculates corrected command voltage V_cmd? by addition of neutral point control compensation quantity V_cmp to three-phase command voltage V_cmd. Limiter LMT3 outputs limiter processed command voltage V_cmd? by liming the output of corrected command voltage V_cmd?. Three-phase to two-phase converter 5 outputs feedback quantities Vd_back, Vq_back by three-phase to two-phase conversion of the limiter processed command voltage V_cmd?. Current control section 2 performs integral control in accordance with quantities resulting from addition of the feedback quantities Vd_back, Vq_back to the deviations.

Abstract: A power conversion controller for electric train in one aspect of the present disclosure includes an active current command value generator, an overhead line voltage detector, an initial value calculator, an adjustment value calculator, an upper limit value setter, and an output limiter. The output limiter outputs a reactive current command adjustment value calculated by the adjustment value calculator as a reactive current command value when the reactive current command adjustment value is equal to or lower than an upper limit value set by the upper limit value setter, and outputs the upper limit value as the reactive current command value when the reactive current command adjustment value exceeds the upper limit value.

Abstract: A system for reducing a resonant oscillation on a direct current bus of a power inverter/converter for an electric machine having a variable frequency drive is disclosed. The system includes a battery, a first capacitor connected in parallel with the battery; an inductor connected in series with the first capacitor; a first diode connected in series with the inductor; a second diode connected in parallel with the inductor and the first diode; a second capacitor connected in series with the first diode; and a starter-generator connected to the second capacitor. During a re-generation mode for charging the battery, a re-generation current flows from the starter-generator to the battery, passing through the first diode and the inductor and bypassing the second diode. During a motor mode, a motor current flows from the battery to the starter-generator, passing through the second diode and bypassing the first diode and the inductor.

Abstract: A switching power supply apparatus, including a power converting device body configured to switch DC input power through a first switching element to thereby store the DC input power in an inductor, and to transfer the stored power to an output capacitor through a second switching element by use of resonance of the inductor, a control circuit configured to drive the first and second switching elements to alternately turn ON or OFF the two switching elements, to thereby resonate the inductor, and an overload detecting circuit configured to detect a load state of the power converting device body based on a peak value or an effective value of a resonance voltage generated from the resonance of the inductor, to thereby control operation of the control circuit.

Abstract: A power converter including one or more converter legs is provided. Each converter leg includes a first string including a plurality of switches coupled to each other in series. The one or more converter legs also include a second string operatively coupled to the first string at a first node and a second node in a parallel configuration, where the second string includes a plurality of switching units, and where a second string of one converter leg of the one or more converter legs is operatively coupled to second strings corresponding to other converter legs in the one or more converter legs.

Abstract: A multilevel inverter includes a first half bridge in series with a second half bridge, each comprising a switch having a channel. The switch is configured to block a substantial voltage in a first direction during a first mode of operation, to conduct substantial current through the channel in the first direction during a second mode of operation, and to conduct substantial current through the channel in a second direction during a third mode of operation. During the third mode of operation, a gate of the switch is biased relative to a source of the switch at a voltage that is less than a threshold voltage of the switch. The inverter may also include a third half bridge. The inverter can be configured such that in operation, switches of the third half bridge are switched at a substantially lower frequency than the switches of the first and second half bridges.

Abstract: An H-bridge micro inverter grid-connected device is invented to solve the problem that failure of any photovoltaic panel on the existing solar photovoltaic system cascade can cause efficiency reduction of the whole photovoltaic panel module. The H-bridge micro inverter grid-connected device comprises a single-chip microcomputer controller, a CPLD controller, a MOSFET full-bridge circuit, a high-frequency transformer, a half-bridge rectifying circuit, an SCR full-bridge circuit and a filter circuit, wherein the MOSFET full-bridge circuit is in the full-bridge type, the high-frequency transformer is a single-phase transformer with a central tap, and the SCR full-bridge circuit is applied. The integral structure above is characterized by the decreasing number of components, the reduction of power switches, and the simplification of the control circuits and driving circuits, so as to decrease the number of full-control switch components, improve the system reliability and reduce the system costs.

Abstract: A high-voltage DC (HVDC) power system and a method of controlling and protecting the HVDC power system includes a plurality of sending-end (SE) modules coupled in electrical series and a plurality of receiving-end (RE) power converter modules electrically coupled to said plurality of SE modules, the RE modules coupled in a switchyard configuration, the switchyard configuration including a plurality of load branches coupled together in electrical series, each load branch including a branch bypass switch configured to bypass load current around an associated load branch, and a branch protection system.

Abstract: A high-efficiency power supply apparatus is provided in light of the reduction of the switching loss. The power supply apparatus connected between the AC power supply and the DC load converts the AC power supplied from the AC power supply to the DC power and supplies it to the DC load. The power supply apparatus comprises the first switching circuit for outputting the switched positive and negative voltages to the primary winding of the transformer, a second switching circuit for supplying the DC power induced in the secondary winding of the transformer and switched to the DC load connected to the second AC terminals, a resonance inductor serial-connected to the primary winding, and a control unit for controlling the switching operations performed by the first and second switching circuits. The control unit substantially short-circuits the second AC terminals by controlling the switching operations performed by the second switching circuit.

Abstract: The invention may enable provision of a method for facilitating operation of an induction heating device, and a pot detection method for an induction heating device and to an induction heating device. The induction heating device is characterized by determining a low point of a resonant cycle on a linking node of a parallel resonant circuit and a switching element, determining a low point voltage at the low point of the resonant cycle and switching on the switching element at the low point of the resonant cycle for a cycle duration that is determined depending on the low point voltage in such a manner that a low point voltage does not exceed a predetermined maximum value in the following resonant cycles.

Abstract: An object of the invention is to accurately detect a state of an object to be heated in a cooking vessel and effectively avoid cooking failure. An induction heating section (13) inductively heats a cooking vessel (11). A vibration detecting section (14) detects a vibration of the cooking vessel (11) via a top plate (12). A vibration waveform extracting section (15) extracts a vibration waveform of a frequency component having a frequency equal to a predetermined multiplication product of an induction heating frequency, from a waveform of the vibration detected by the vibration detecting section (14). A determining section (16) determines a state of an object to be heated, based on the vibration waveform extracted by the vibration waveform extracting section (15).

Abstract: A power converter module is disclosed, which is an all-digital module. The power converter module includes a reference voltage generation unit, a voltage loop control unit, a current loop control unit, an input voltage compensation unit, and a pulse width modulation generation unit, to transfer input power to stable output power for providing power to an external loading device through driving bridge switch unit with external driver. The voltage loop control unit and the current loop control unit contain a proportion-integral-differentiation controller for receiving signal related to voltage and current of loading device to form voltage control loop and current control loop. The pulse width modulation generation unit contains function of deciding necessary stop time to improve quality of output power and decrease the effect of input power and loading variation, and to provide stable sine-waveform output power to the external loading device.

Abstract: An uninterruptable power supply (UPS) designed to switch power inputs between an alternating current mode and a battery mode by adjusting the amplitude and/or frequency windows of the input voltage so that the uninterruptible power supply accepts the unstable voltage and/or frequency. This prevents the uninterruptible power supply to switch back to the battery mode during a transfer time between the battery mode and the AC mode. The uninterruptable power supply includes a control circuit. The control circuit modifies the monitored value and/or actual amplitude and/or the frequency window when unstable amplitude and/or an unstable frequency are detected at the input terminal of the input voltage.

Abstract: An embodiment of a multidirectional signal converter includes first and second converter nodes, a transformer, and first and second stages. The transformer includes first and second windings, and the first stage is coupled between the first converter node and the first winding of the transformer. The second stage includes a first node coupled to the second converter node, a second node coupled to a node of the second winding of the transformer, and a filter node, is operable as a boost converter while current is flowing out from the second converter node, and is operable as a buck converter while current is flowing out from the first converter node. For example, in an embodiment, such a multidirectional signal converter may be a bidirectional voltage converter that handles power transfer between two loads. Such a voltage converter may have improved conversion efficiency and a smaller size and lower component count as compared to a conventional multidirectional voltage converter.

Abstract: In order to provide a method for regulating a reactive power compensator, which is connected to an alternating current line having multiple phases, wherein for each phase an actual voltage V12, V23 and V31 present thereon is detected and from the actual voltages V12, V23 and V31 a counter system actual fraction is calculated. A control circuit suppresses the counter system actual fraction. A feedback loop determines the level of suppression of the counter system actual fraction with the help of controlled parameters. The method enables an adjustment of the counter system that is largely independent from operating staff. Accordingly, a comparator unit compares the counter system actual fraction to the counter system target fraction and defines the controlled parameters as a function of the comparison.

Abstract: A power electronic assembly includes a pair of thermally and electrically conductive plates, and semiconductor switching elements positioned between contact surfaces of the pair of conductive plates. A first of the semiconductor switching elements is positioned at a first region of the conductive plates, and a second of the semiconductor switching elements positioned at a second region of the conductive plates. At least one of the conductive plates includes an aperture positioned between the first region and the second region of the conductive plates, such that in a compressed state, a contact surface of the conductive plate associated with the first region is substantially parallel to and offset from that of the second region in a direction parallel to the direction of compression.

Abstract: An electric vehicle includes a control unit having overcurrent generation judgment unit, inverter selection unit, and inverter drive control unit. The overcurrent generation judgment unit judges whether an overcurrent is generated in an inverter for generation or an inverter for travel. When an overcurrent is generated in one of the inverters, the inverter selection unit selects the other inverter to be driven. The inverter drive control unit stops the driving of the one inverter and drives the other inverter to drive a travel motor or a generator.

Abstract: A power supply and methods are provided. In one implementation, the power supply includes a switching circuit and a converter. The switching circuit includes a first transistor and a second transistor, and the converter includes a capacitor and an inductor. The switching circuit alternately switches an input voltage to the converter. The power supply further includes a controller operable to adjust a switching frequency of the first transistor and the second transistor to substantially match a resonant frequency of the capacitor and the inductor.

Abstract: In general, in one aspect, the invention relates to a method for delivering a controlled voltage. The method involves, during a first electric pulse delivered to a primary transformer, holding a first switching section open to isolate the controlled voltage, where the first electric pulse creates a first magnetic flux in a core of the primary transformer, and where the first magnetic flux generates a direct current (DC) magnetizing current. The method further involves receiving the controlled voltage from a voltage source using the DC magnetizing current at a first switching section, and upon termination of the first electric pulse, closing the first switching section to deliver the controlled voltage to the primary transformer.

Abstract: An apparatus for monitoring current for a motor drive including at least high-side and low-side switching transistors includes a driver circuit for driving a gate of the low-side switching transistor. First circuitry measures a drain to source voltage across the low-side switching transistor and generates a voltage output responsive thereto. Second circuitry has a first state of operation that samples the voltage output of the first circuitry when the low-side switching transistor is turned on and has a second state of operation to sample the voltage output of the first circuitry when the low-side switching transistor is turned off. The second circuitry further generates a monitored output current responsive to the sampled voltage output.

Abstract: An exemplary embodiment includes a system for measuring and controlling a thyristor comprising a thyristor, a Rogowski coil in operable communication therewith the thyristor, and a processor operative to receive signals from the Rogowski coil, determine a direct current value of the thyristor, and control the thyristor.

Abstract: A method of controlling an inverter to includes determining the components of a phasor representing the output current from the inverter in a fixed reference system; determining the components of the current phasor in a reference system rotating at a velocity equal to the velocity of rotation of the phasor representing the grid voltage; and comparing the components of the current phasor in the rotating reference system with a reference, again expressed in the rotating reference system, to determine an error signal, by means of which the inverter is controlled.

Abstract: In a control system for a static var compensator that performs phase control of a current of a reactor for each phase by a thyristor and thus controls reactive power, a detecting unit that detects a tertiary harmonic current flowing through each phase of the static var compensator is provided, and on the basis of the tertiary harmonic current flowing through each phase detected by the detecting unit, the thyristor of each phase is controlled so that the quantity of generated tertiary harmonic current of each phase becomes equal, and therefore an outflow of the tertiary harmonic current toward a system can be restrained by an inexpensive method.

Abstract: Voltage inverter provided with four switching cells (Q1 to Q4) to be connected to the terminals of a DC voltage source (Vdc), each comprising two semiconductor switches (I11, I12, I21, I22, I31, I32, I41, I42) installed in series, these switches having a common point (A0) to be connected to an AC current source (Mac) with three phases (p1, p2, p3) and a neutral (n), the connection being made onto one phase (p1, p2, p3) for three of the cells (Q1, Q2, Q3) and onto the neutral (n) for the fourth cell (Q4). Each cell (Q1 to Q4) cooperates with a semiconductor electrical isolating device (S1, (S2.1 and S2.2)) to be put into a turn-off state if the cell should fail, this isolating device (S1, (S2.1 and S2.2)) being arranged either on the connection to the AC current source (Mac), or on connections to the terminals of the DC voltage source (Vdc).

Abstract: A system for controlling a soft start for a switching power converter includes a digital controller that enables the programming of a plurality of input voltage profiles during a soft start condition of the switching power converter. The programming of the plurality of input voltage profiles is parameterized by a control parameter. A microcontroller determines the control parameter used by said digital controller and operates independently of the operation of the digital controller.

Abstract: In an electric car control apparatus for driving an induction motor, detection accuracy of a DC voltage is improved. A DC power supply device is provided which has a maximum potential terminal A, an intermediate potential terminal B, a minimum potential terminal C, an upstream side capacitor 6 between the maximum potential terminal A and the intermediate potential terminal B, and a downstream side capacitor 7 between the intermediate potential terminal B and the minimum potential terminal C. Also, an overvoltage suppression part is provided which includes a resistor 8 and a thyristor 9 between the maximum potential terminal A and the minimum potential terminal C.

Abstract: A power source supplies an input voltage. A voltage conversion circuit converts the input voltage from the power source into an operating voltage to be used to drive an electric load. A detection circuit measures an insulation resistance value on the output side of the voltage conversion circuit. A control circuit controls a voltage conversion ratio in the voltage conversion circuit, which is expressed as a ratio of the operating voltage to the input voltage, in accordance with the insulation resistance value detected by the detection circuit. The control circuit sets the voltage conversion ratio such that the operating voltage becomes lower at the time of degradation of an insulation resistance than at the time of normal operation thereof.

Abstract: A method for triggering a high voltage solid state switch comprised of a set of thyristors connected in series. Initiating switch turn-on requires command triggering of only the lowest voltage thyristor, thereby eliminating the need for expensive high voltage pulse transformers or optically isolated triggers. Triggering of one thyristor causes a redistribution of voltage across the switch, generating a current flowing through the snubber circuit across each untriggered thyristor. This current is coupled to the gate of each thyristor causing all of them to turn on simultaneously. This results in an inexpensive method for triggering a high voltage solid state switch.

Abstract: Timing of zero voltage in zero-voltage detector for detecting zero voltage of a commercial power supply 1 is predicted and input from the zero-voltage detector 6 is received only for a given time before and after the predicted timing, whereby overvoltage and overcurrent caused by a zero point shift can be prevented. Thus, it is provided a magnetron drive power supply which is excellent in stability for change in the power supply environment such as noise or instantaneous power interruption.

Abstract: A method for control of an extinction angle of a line-commutated converter in dependence on a minimum reference value for the extinction angle. The converter has a plurality of valves, each one of the plurality of valves having at least one semiconductor element capable of being fired, and the device has a unit for generating firing control pulses for a commutating valve in dependence on the minimum reference value of the extinction angle according to a given criterion for commutation of a direct current through the converter. The device has a unit for continuously forming an operating value of recovery time for the semiconductor element of a decommutating valve, and a unit for forming the minimum reference value of the extinction angle in dependence of the operating value.

Abstract: Timing of zero voltage in zero-voltage detector for detecting zero voltage of a commercial power supply 1 is predicted and input from the zero-voltage detector 6 is received only for a given time before and after the predicted timing, whereby overvoltage and overcurrent caused by a zero point shift can be prevented. Thus, it is provided a magnetron drive power supply which is excellent in stability for change in the power supply environment such as noise or instantaneous power interruption.

Abstract: A current source inverter (1) comprises a bridge circuit (2) having a plurality of bridge paths (5), in each of which a controllable power semiconductor component (6) is arranged. In the case of such an inverter, a loss in performance on account of inductance-dictated overvoltages during the turn-off of the power semiconductor components (6) is avoided by virtue of the fact that the controllable power semiconductor component (6) is avalanche-proof at least under loading in the forward direction.

Abstract: Thyristor-controlled series capacitor equipment (CEQ), intended for connection between an ac network (NET) and a converter (CONV), connected thereto, for conversion between alternating current ((IT) and high-voltage direct current (Id), with a controllable semiconductor valve (TYSW), has control equipment with control means (32) which, in dependence on a synchronization signal (&PHgr;SYNC), form firing pulses (TP1,TP2) for control of the semiconductor valve. The converter has a control device (CTR1) which forms a control-angle order (&agr;-ORD) for phase-angle control of the converter, related to the phase position for a voltage (U12) at a chosen connection point (J2).

Abstract: An electric motor to be used with a termination network that is integral with the motor and connected to the motor's supply motor lines for reducing voltage between a motor terminal and a transmission line connected to a pulse width modulated drive when high frequency surges, or spikes, are present. Further, the termination network will not adversely effect sinusoidal performance ratings of the motor on which it is used. In addition, since the termination network is integral with the motor, the termination network assembly can be installed during assembly of the motor, thus lowering the cost of installation.

Abstract: An improved commutation circuit configured to arrest and dissipate energy which may be reflected from a magnetic pulse compression network. The commutation circuit includes an energy storage capacitor for storing energy, a capacitor charging unit for charging the energy storage capacitor, a power supply protection circuit configured for isolating reverse voltages from the output of the capacitor charging unit, a series switch configured for conducting current in the forward direction and blocking current in the reverse direction to and from the energy storage capacitor, a magnetic assist device configured for isolating the reverse voltage from the switch, a trigger circuit configured for transmitting a trigger pulse signal to the switch to allow the transfer of reflected energy to the energy storage capacitor and a power supply configured for biasing the magnetic assist device.

Abstract: An electromagnetic, compatible, clocked amplifier for d.c./a.c., current amplification including, for a single phase, a transistor power amplifier having at least one first switching transistor and at least one second switching transistor, and two diodes connected in parallel with respective ones of the first and second transistors; a set value adjuster; an output filter connected with an output of the transistor power amplifier and having at least one current limiting resistor, one filter inductance and one charging capsitor, and two power thyristors polarized in accordance with respective voltage signs and connected in parallel with the current limiting resistor.

Abstract: An apparatus for essentially eliminating transmission line reflected waves and standing waves and for reducing common mode transient currents for use with a three phase motor controller, the apparatus including a common mode choke in series with a filter network between an inverter and a motor, the filter including three inductors and three resistors, the inductors and resistors together forming three inductor-resistor pairs, each pair including an inductor in parallel with a resistor, each pair linked to a separate one of three transmission supply lines which link the inverter to the motor, values of the resistors and inductors selected according to transmission line theory.

Abstract: A method and arrangement for controlling the output of electrical consumers connected to ac line voltage, especially of electric motors and the like, in which the output is changed by changing the phase control of the electric alternating magnitude supplied to the consumer. The extent of the firing angle determining the extent of the phase control is varied toward larger or smaller values around the given reference value of the firing angle, which reference value corresponds to the desired power consumption, so that asymmetry of the firing angle is produced with respect to time between two successive full waves, whereby odd-numbered harmonics are sharply reduced as even-numbered harmonics slowly increase.

Abstract: A power conversion system including a plurality of converter transformers. AC side windings of the converter transformers are connected in series for connecting to an AC power system. The power conversion system further includes a plurality of series connected voltage source type self-commutated converters for converting AC power into DC power or DC power into AC power. Each of the voltage source type self-commutated converters is connected to one of DC side windings of the converter transformers, respectively. The power conversion system further includes a plurality of DC voltage sources. Each of DC output sides of the voltage source type self-commutated converters is connected to one of the DC voltage sources, respectively.

Abstract: An uninterruptible power supply (UPS) system comprising an inverter for converting a DC voltage into an AC voltage comprising a full-bridge circuit having four silicon controlled rectifier (SCR) switches, two pulse control circuits for generating control voltage signals to turn on alternate pairs of said switches, a time sequencing circuit, and a power switch circuit. The full bridge circuit is directly connected to a positive DC input terminal and is coupled through the power switch circuit to a negative DC input terminal. The time sequencing circuit generates a first pulse signal for controlling the first pulse control circuit and a second pulse signal for controlling the second pulse control circuit so that the first pulse signal and the second pulse signal being in phase opposition. The time sequencing circuit further generates a third pulse signal for controlling the power switch circuit.

Abstract: A three-phase dc to-ac power inverter includes a dc power source with a first dc node for positive voltage, a second dc node for negative voltage, and a third dc node for zero voltage. A set of three-level pole circuits are connected to the first dc node, the second dc node, and the third dc node of the dc power source. A control circuit, responsive to an inverter voltage vector reference demand signal with a voltage magnitude reference demand component and a voltage phase reference demand component, generates pole control signals for the three-level pole circuits using logic circuitry which combines phase indexed digital waveform values stored in a pair of lookup tables. The pole control signals force the three-level pole circuits to generate a set of phase-shifted waveforms with zero voltage components. The phase-shifted waveforms are combined by a set of transformers to produce a three-phase output voltage with a harmonic content lower than the harmonic content of the phase-shifted waveforms.

Abstract: A control device for a PWM controlled converter having a voltage control portion for comparing with a voltage set value a detected value of a DC voltage output from the PWM controlled converter, connected through reactors to a 3-phase AC power source, for controlling AC input currents supplied from the 3-phase AC power source, to thereby produce current reference signals; an AC reference signal generating portion for generating AC reference signals synchronized with the 3-phase AC power source; a current instruction portion for producing current instruction signals formed by varying the amplitudes of the AC reference signals output from the AC reference signal generating portion in accordance with the current reference signals, and a current control portion for producing control signals to the PWM controlled converter so that the AC input currents vary as instructed by the current instruction signals.

Abstract: A power converter comprises two main switches connecting an output either to the positive rail or to the negative rail. Two freewheel diodes for maintaining the current in the load, two snubbers and an auxiliary circuit including an auxiliary inductor in series with two auxiliary switches connected between the output and a mid-point of a capacitive voltage divider supplying a median voltage. Any error of the median voltage relative to its nominal value is evaluated and the main switches are additionally commanded, depending on the direction of the error, for a time period dependent on the amplitude of the error, in order to cause an additional current in the auxiliary circuit to correct the error at least in part.

Abstract: The MOSFETs or IGBTs of respective arms of an electronic inverter are in series with SCRs or TRIACs triggered into conduction during intervals of intended conduction of the respective MOSFETs or IGBTs connected to the high level rectifier terminal. The piloting of the SCRs or TRIACs is effected from the piloting of the MOSFETs or with delay or in a conditional manner. The circuit eliminates the effective transience on the inverter output.

Abstract: A control system for a power conversion system composed of a plurality of unit converters and a transformer for connecting AC outputs of the unit converters in series. The control system includes a unit for detecting an AC system voltage at the primary winding of the transformer, a unit for generating a command voltage vector of a voltage output from the power conversion system at the primary winding of the transformer based on the AC system voltage, and an actual voltage vector selecting unit for preparing a plurality of actual voltage vectors of voltages output from the power conversion system at the primary winding of the transformer, and selecting one of them as a selected actual voltage vector.

Abstract: A high power inverter pole for a voltage sourced inverter suitable for providing compensation in electric power transmission and distribution systems, has a positive switching valve and a negative switching valve connected between closely spaced dc-source terminal, respectively, and a common ac terminal to form a current loop with minimum loop area thereby reducing stray loop inductance and limiting the overshoot voltage on serially connected electronic switches which make up the valves. In a preferred embodiment, the valves are mounted on opposite sides of the web of an insulative I-beam. The electronic switches are incorporated in modular switching units connected in series by C-channel connecting conductors having flanges bolted to the I-beam flanges. The modular units include broad, flat conductors bolted through end flanges to the C-channel connecting conductors. The electronic switches and anti-parallel diodes of the modular units are clamped between these broad, flat conductors.

Abstract: A neutral point clamped (NPC) inverter control system including a DC power source to output DC voltage having a neutral point, an NPC inverter to convert the DC voltage into AC voltage in three phases through a PWM control, a mode selecting unit to decide a first and a second PWM modes by comparing amplitude of voltage reference with a prescribed value that is defined by a minimum pulse width, a first voltage reference conversion means to add a prescribed bias value at which a polarity changes to positive/negative within a fixed period to secure the minimum pulse width to voltage references in respective phases in a first PWM mode, a second voltage reference conversion means to fix the voltage reference in one phase by a value that secures the minimum pulse width when voltage reference in one phase is smaller than a prescribed value that is defined by the minimum pulse width in a second PWM mode and correct voltage references of other two phases so as to make line voltage to a value corresponding to the volta