JP2012178938A - Power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion system, having unit power converters connected in parallel using DC circuits and AC circuits, capable of suppressing a vibrating current running through the DC circuits comprised of the connected unit power converters by switching the unit power converters connected in parallel, and zero-phase currents running through a ground circuit when the power converter transmits electric power to an AC system through a transformer with a neutral point grounded.SOLUTION: In the power conversion system, a gapped reactor is connected to each of a positive electrode and a negative electrode of a DC terminal of a unit power converter, and the unit power converter is connected to the other unit power converter through the reactor.

Description

  The present invention relates to a power conversion system.

  In recent years, a technique for power conversion using a semiconductor switching element has been widely used. In this technology, AC power is turned on / off by a semiconductor switching element and then smoothed by a capacitor to obtain a DC current between the positive terminal and the negative terminal, or conversely, DC power is switched to semiconductor switching. AC power can be obtained by conducting / terminal the element.

  Combining the above techniques, for example, AC power is turned on / off with a semiconductor switching element and then smoothed with a capacitor to obtain DC power. AC power having a frequency can be obtained.

  In this case, since an oscillating current is generated in the process of obtaining a direct current, a technique for inserting a reactor and a resistor has been devised to suppress the oscillating current. Such a technique is described in Patent Document 1, for example.

  On the other hand, in recent years, the capacity of renewable energy systems has been increasing, and the capacity of semiconductor power converters that convert electric power generated from solar panels and wind power generators has also increased. Since the output specifications of the power converter differ depending on the installed system capacity, a power converter that converts AC power into DC power (or converts DC power into AC power) to support various capacity specifications. A technique has been devised in which the unit power converters are configured as unit power converters and connected in parallel. Such a technique is described in Non-Patent Document 1, for example.

JP 2003-319639 A

`` ABB low voltage wind turbine converters-ACS800, liquid-cooled 0.6 to 6 MW '', ABB, 2010

  In the technique disclosed in Patent Document 1 above, a wiring is formed in which a semiconductor switching element that converts alternating current into direct current and a semiconductor switching element that converts direct current into alternating current are directly connected. Since zero-phase current can flow, the temperature of the wiring and the electrical component to which the wiring is connected due to generation of the zero-phase current rises, and in particular, the life of the capacitor is shortened.

  Further, in the technique shown in the above non-patent document, an oscillation current flows through a DC circuit portion connecting the unit power converters by switching operations of the unit power converters connected in parallel, and the unit power converters are built in the unit power converters. This increases the heat generated in the capacitor and circuit wiring, and shortens the life of the capacitor.

  In particular, when the power converter is an inverter for solar power generation or an inverter for wind power generation that transmits power to an AC system via a transformer with a neutral point grounded, solar power connected to the power converter The stray capacitance between the panel and the ground and the stray capacitance between the generator winding and the generator housing are large, and switching is performed via the stray capacitance, the power converter, the transformer neutral point, and the ground (ground circuit). Zero phase current including frequency flows. Since the zero-phase current flows through the DC circuit, the DC circuit wiring and the components connected to the DC circuit wiring are further heated, and in particular, the life of the DC capacitor is further shortened.

  An object of the present invention is to provide a power conversion system that can suppress a zero-phase current or an oscillating current flowing in a circuit and maintain a long life of a circuit component.

  In order to achieve the above object, in the present invention, DC power applied to a first DC side terminal composed of a first positive DC terminal and a first negative DC terminal is supplied to the first semiconductor switching element. A first power conversion unit for converting into AC power, a second DC side terminal composed of a second positive DC terminal and a second negative DC terminal, and a second semiconductor switching element, The second semiconductor switching element converts alternating current power or direct current power and outputs it to the second direct current side terminal, or converts direct current power applied to the second direct current side terminal into alternating current power. A second power conversion unit, a capacitor for smoothing fluctuations associated with a switching operation of the first switching element or the second switching element, the first positive DC terminal, and the second Positive DC terminal Connected via a reactor, the first and the negative DC terminal, and configured to connect through the second reactor a negative side DC terminal.

  According to the present invention, it is possible to suppress the zero-phase current or the oscillating current flowing in the circuit and to keep the life of the circuit component long.

FIG. 3 is an explanatory diagram of a power converter according to the first embodiment. Explanatory drawing of the power converter of Example 2. FIG. Explanatory drawing of the power converter of Example 2. FIG. 1 is an explanatory diagram of a single-machine power converter according to Embodiment 1. FIG. Explanatory drawing of the chopper of Example 2. FIG. Explanatory drawing of the power converter of Example 2. FIG. Explanatory drawing of the reactor inserted in the DC circuit of the power converter of Example 1. FIG. Explanatory drawing of the reactor inserted in the DC circuit of the power converter of Example 1. FIG. Explanatory drawing of the power converter of Example 2. FIG. Explanatory drawing of the permanent magnet generator to which the power converter of Example 1 is connected. Explanatory drawing of the gate signal calculation calculating part of the power converter of Example 1. FIG. The zero phase current flow path explanatory drawing in the power converter of Example 1. FIG. The zero phase current flow path explanatory drawing in the power converter of Example 1. FIG. FIG. 3 is an explanatory diagram of a power converter according to the first embodiment. FIG. 3 is an explanatory diagram of a power converter according to the first embodiment. 4 is a timing chart of an on-delay generation circuit of the power converter according to the first embodiment.

  The details of the present invention will be described with reference to the drawings.

  This embodiment will be described with reference to FIG.

<Outline configuration>
The power converter shown in FIG. 1 is a wind power generator for power generation composed of a plurality of unit power converters. Reference numeral 1 is a power converter of the present embodiment, reference numeral 80 is a blade, reference numeral 40 is a permanent magnet generator, reference numeral 70 is a shaft (power transmission shaft) that transmits rotation of the blade 80 to the permanent magnet generator rotor, and reference numeral 30 is It is a connection transformer for connecting the power converter 1 to the power system 10000. The secondary neutral point of the interconnection transformer 30 is grounded to fix the potential.

<Outline function>
The power converter 1 includes a converter 200 that converts AC power output from the permanent magnet generator 40 into DC power, and an inverter 100 that converts the DC output power of the converter into AC power having the same frequency as the power system and transmits the AC power to the system. And a control device 1000 for controlling the inverter 100 and the converter 200.

  The blade 80 converts wind energy into rotational energy and transmits the rotational energy to the permanent magnet generator 40 via the shaft 70. The configuration of the permanent magnet generator 40 is shown in FIG.

  The shaft 70 is mechanically connected to the rotor 40r of the permanent magnet generator 40, and the shaft 70 rotates the rotor 40r of the permanent magnet generator 40. The rotor includes a permanent magnet 40m, and a magnetic flux generated by 40m links the stator windings 40sa, 40sb, and 40sc of the permanent magnet generator 40 to generate an induced voltage in the stator winding.

  The permanent magnet generator 40 is grounded to prevent the operator from receiving an electric shock.

  Returning to FIG. 1, the description of the power converter 1 of the present invention will be continued.

  The converter 200 is a power converter constituted by an IGBT, and outputs a desired AC voltage to the permanent magnet generator 40 by turning on and off the IGBT based on a gate signal 1000G2 output from the control device 1000. An electromotive force generated by the rotation of the rotor 40r and an AC voltage output from the converter 200 are applied to the stator winding 40s of the permanent magnet generator 40. A generator current determined by the difference between the induced power and the AC voltage and the stator winding impedance flows through the winding.

  Therefore, control device 1000 outputs a suitable gate signal (IGBT gate signal) 1000G2 to permanent magnet generator 40, so that converter 200 can receive desired AC power from permanent magnet generator 40.

  In the present embodiment, a permanent magnet generator is shown as the generator, but the generator may be a synchronous generator to which a DC excitation current is supplied from the outside of the generator.

  Inverter 100 converts the DC power converted by converter 200 into AC power by switching the IGBT in inverter 100, and outputs the AC power to power system (AC system) 10000.

  Specifically, by outputting a gate signal (IGBT gate signal) 1000G1 from the control device 1000 so that the inverter 100 outputs an alternating voltage with an advanced phase with respect to the inverter 100 side terminal voltage of the transformer 30, The inverter 100 converts the DC power rectified by the converter 200 into AC power and outputs the AC power to the system.

<Detailed configuration>
The configuration of the power converter 1 will be described in detail below.

<Connection>
The inverter 100 includes inverters 10 and 11 that are unit power converters, and reactors 51, 52, 55, and 56. One end of the reactor 51 is connected to the positive DC terminal 10P of the inverter 10, and one end of the reactor 52 is connected to the negative DC terminal 10N of the inverter 10.

  Similarly, one ends of reactors 55 and 56 are connected to the positive DC terminal 11P and the negative DC terminal 11N of the inverter 11, respectively.

  Converter 200 includes converters 20 and 21 and reactors 53, 54, 57, and 58 which are unit power converters. A reactor 53 is connected to the positive DC terminal 20P of the converter 20, and a reactor 54 is connected to the negative DC terminal 20N of the converter 20.

  Similarly, one ends of reactors 57 and 58 are connected to positive DC terminal 21P and negative DC terminal 21N of converter 21, respectively.

  Reactors 51, 53, 55, and 57 have other ends connected to positive DC wiring 8001, and reactors 52, 54, 56, and 58 have other ends connected to negative DC wiring 8002.

<Converter configuration details>
The inverters 10 and 11, the converter 20, and the converter 21 that are unit power converters have the same main circuit configuration. The main circuit configuration will be described with reference to FIG. 4 taking the inverter 10 as an example.

  The inverter 10 includes IGBTs 10a, 10c, 10e, 10g, 10i, and 10k and free-wheeling diodes 10b, 10d, 10f, 10h, 10j, and 10l connected in reverse parallel to the IGBT, a three-phase power conversion unit, and a DC smoothing capacitor 10m, and AC reactor 10n. The AC reactor 10n is a tripod reactor.

  The IGBT is ON / OFF controlled by a gate signal 1000G1 output from the control device 1000, and outputs an AC voltage obtained by pulse-width-modulating the voltage across the DC smoothing capacitor 10m to the power conversion unit side of the reactor 10n.

  As shown in FIG. 11, the gate signal is created by comparing the magnitude of an AC output voltage command value calculated in the control device 1000 with a triangular wave that is a carrier wave.

  Specifically, a carrier wave vtri that is an output of a carrier wave calculator (not shown) and a U phase, V phase, and W phase voltage command value vu_ref that are outputs of a U phase, V phase, and W phase voltage command value calculator (not shown). vv_ref and vw_ref are input to the comparators 1000c1, 1000c2, and 1000c3, respectively. Comparators 1000c1, 1000c2, and 1000c3 output 1 when the voltage command value is greater than the carrier wave vtri, and 0 otherwise.

  The inverters 1000i1, 1000i2, and 1000i3 output values obtained by logically inverting the outputs of the comparators 1000c1, 1000c2, and 1000c3.

  The gate signal of the positive-side IGBT corresponds to the output signal of the comparator, and the gate signal of the negative-side IGBT corresponds to the output signal of the inverter, but the IGBT requires a finite time to turn on or turn off. In order to avoid a short circuit of the DC smoothing capacitor 10m via the IGBT through the IGBT during this finite time, the gate signal is applied only when the output of the comparator and the inverter is turned on as shown in FIG. The signals are input to the on-delay circuits 1000d1, 1000d2, 1000d3, 1000d4, 1000d5, and 1000d6 that delay Td seconds, respectively, and the output is output as a gate signal to the unit power converter. Here, Td is usually several microseconds.

<Description of operation>
The functions of this embodiment and the functions thereof will be described in detail below.

The feature is that a reactor is provided on both the positive electrode and the negative electrode of the DC terminal of the unit power converter.
By providing the reactor, it is possible to limit the oscillating current flowing in the DC circuit between the unit power converters. At the same time, the zero-phase current flowing through the power converter 1 can be suppressed.

  Hereinafter, the vibration current suppression effect and the zero-phase current suppression effect will be described in order with reference to the drawings.

  First, the vibration current suppressing effect will be described.

  The inverter 10 and the inverter 11 have an AC terminal and a DC terminal connected in parallel. There are individual differences in the time required for IGBT switching and the impedance of the reactor connected to the AC terminal (AC reactor 10n in the inverter 10). Even if the same gate signal is given to the inverters 10 and 11, the inverters 10 and 11 A difference occurs in the current flowing into the DC circuit from the power conversion unit, a difference occurs in the terminal voltages of the DC smoothing capacitors 10m and 11m of the inverter 10 and the inverter 11, and an oscillating current is generated.

  Since the current flowing from the power converter to the DC circuit changes every time the IGBTs of the inverters 10 and 11 are switched, the oscillating current of the DC circuit is maintained.

  When the reactors (DC reactors) 51, 52, 53, 54 are not inserted, an oscillating current having a resonance frequency component determined by the inductance of the DC smoothing capacitors 10m, 11m and the wiring connecting the DC smoothing capacitors flows in the DC circuit. When the resonance frequency of this circuit is in the vicinity of the IGBT switching frequency, an excessive ripple current flows in the DC circuit, causing abnormal overheating of the DC circuit and the smoothing capacitor.

By inserting the reactors (DC reactors) 51, 52, 53, 54, it becomes possible to adjust the resonance frequency of the DC circuit, and an excessive vibration current can be avoided.
Specifically, the resonance frequency determined by the capacitances of the capacitors 10 m and 11 m and the inductances of the reactors (DC reactors) 51, 52, 53 and 54 is made lower than the switching frequency of the inverters 10 and 11, thereby flowing in the inverter 100. Generation of an excessive vibration current can be avoided.

  Moreover, by making this reactor into a reactor with an iron core, the hysteresis loss which generate | occur | produces when an oscillating current flows through this reactor has an effect which accelerates | stimulates attenuation | damping of this oscillating current.

  Furthermore, by providing a gap in the reactor with the iron core, it is possible to avoid the iron core magnetic saturation due to the direct current and to obtain the vibration current attenuation effect due to the increase in stray loss.

  The structure of the reactor (DC reactor) 51 is demonstrated using FIG. 7, FIG. The reactor of a present Example is an outer iron type reactor which arrange | positions a magnetic body around a conductor.

  The positive circuit 8001 of the DC circuit 800 is connected to the copper bar 5102 which is the main current circuit of the reactor via the copper bar 5106, and the DC current flows through the copper bar 5102 and the copper bar 5105 and flows into the inverter 10.

  Iron cores 51011 and 51012 are in contact with the copper bar 5102 through a nonmagnetic material 5200. The iron cores 51011 and 51012 are fixed by a nonmagnetic material 5300. The iron cores 51011 and 51012 are fixed with a nonmagnetic material (not shown), and a gap is provided between the iron cores (magnetic materials) 51011 and 51012. In order to avoid magnetic saturation due to direct current and to generate floating loss due to leakage magnetic flux, this gap is provided with a gap of 0.5 mm, for example.

  A wiring 5110 for fixing the potential is connected to the iron core 51011 and connected to the copper bar 5102. The iron cores 50111 and 51012 are mechanically fixed by a non-magnetic material (stainless steel strip) 5300. The potential of the iron core 51012 is fixed to the copper bar 5102 via the stainless steel strip, the iron core 51011, and the wiring 5110.

  The copper bar 5102 is fixed to the housing of the power converter (power converter) 1 via insulators 5103 and 5104. The housing is grounded to avoid electric shock of the operator.

  With this configuration, the iron core potential can be fixed to the copper bar 5102 through which the main current flows, so that the insulation between the housing and the iron core is facilitated. Further, since the direct current reactor is divided into the positive electrode and the negative electrode, the necessary space per reactor can be reduced, so that the degree of freedom in installing the reactor in the case of the power converter 1 is increased.

  Next, the zero phase current suppression effect will be described.

  Converter 200 outputs an AC voltage corresponding to the induced voltage frequency and amplitude of permanent magnet generator 40 that varies depending on the wind speed, to permanent magnet generator 40. On the other hand, the inverter 100 outputs an AC output voltage to the transformer side 30 according to the frequency and amplitude of the interconnected system.

  Therefore, the AC voltage output from inverter 100 and the AC voltage output from converter 200 are different, and the switching timings of the IGBTs in inverter 100 and converter 200 are also different.

  When the switching states of the IGBTs of the inverter 100 and the converter 200 are different, there is a difference between the AC terminal zero-phase voltages of the inverter 100 and the converter 200. Inside the wind power generation system, the power converter (power converter) 1, the transformer 30 A zero-phase current flows through the point, the ground, the casing of the permanent magnet generator 40, the stray capacitance between the casing of the permanent magnet generator 40 and the stator windings 40sa, 40sb, 40sc, and the stator winding.

  As an example, FIG. 12 shows an equivalent circuit of this embodiment when all the positive-side IGBTs of the inverter 100 are on and the negative-side IGBT of the converter 200 is on, and all the negative-side IGBTs of the inverter 100 are on and the positive-side IGBT of the converter 200 FIG. 13 shows an equivalent circuit of this embodiment when all are on. Here, the inverter 100 is represented by a model in which the inverters 10 and 11 are degenerated. A circuit in which a current flows is indicated by a solid line, and a circuit in which a current does not flow due to the turned off IGBT is indicated by a broken line. The same applies to the converter 200.

  The permanent magnet generator 40 is configured such that the stator windings 40sa, 40sb, and 40sc have a leakage inductance, a stray capacitance distributed constant circuit 40seq between the windings and the casing, and the permanent magnet 40m. It is represented as a series circuit of induced voltage 40e0 generated in the line.

  In FIG. 12, the DC smoothing capacitors of the inverter 100 and the converter 200 serve as a power source, and the inverter 100, the transformer 30, the neutral point of the transformer 30, the ground, the permanent magnet generator 40 housing, the stray capacitance of the permanent magnet generator 40, and the fixed Zero-phase current flows through the child windings 40sa, 40sb, 40sc and the converter 200.

  In FIG. 13, the DC smoothing capacitor serves as a power supply in the same manner as in FIG. 12, but a zero-phase current flows in the opposite direction to FIG. 12 because the switching state of the IGBT is different.

  Thus, the zero-phase current flowing through the power converter 1 becomes an alternating current whose polarity changes depending on the switching state of the IGBT.

  In a several megawatt wind power generation system, the stray capacitance between the casing of the permanent magnet generator 40 and the stator windings 40sa, 40sb, and 40sc is large, and the zero-phase current easily flows.

  Further, in the case of a power converter having a switching frequency of several kHz, the impedance of the stray capacitance becomes relatively small, and the zero-phase current via the stray capacitance of the permanent magnet generator 40 becomes easier to flow.

  Furthermore, when the AC reactors of inverters 10 and 11 and converters 20 and 21 are tripod cores, the inductance with respect to the zero phase is small, and a larger zero phase current flows.

  Here, for reference, in comparison with the power converter disclosed in Patent Document 1, in the power converter disclosed in Patent Document 1, a reactor is inserted only in the positive or negative side of the DC circuit 800. Yes. For this reason, the zero-phase current flows through a circuit in which no reactor is inserted, and a great effect of suppressing the zero-phase current cannot be expected.

  On the other hand, since the power converter 1 of the present embodiment includes reactors in both the positive and negative electrodes of the DC circuit, the inductance of the high-frequency zero-phase current circuit is increased, so that the high-frequency zero-phase current is effectively suppressed. be able to. Moreover, when the reactor is a reactor with a gap, when an oscillating current of an LC circuit constituted by the reactor and the stray capacitance of the permanent magnet generator 40 is generated, a hysteresis loss generated in the reactor of the oscillating current is reduced. The damping effect of the oscillating current occurs due to the floating loss, and a reduction in the oscillating current can be expected.

  For the above reasons, the power converter according to the present embodiment can reduce both the DC oscillating current between the single-machine power converters and the zero-phase current flowing through the power converter.

  In this embodiment, the power converter 1 is connected to a permanent magnet generator. However, when the connected generator is an AC excitation generator and the rotor shaft is grounded via a slip ring, Has the same effect.

  Moreover, the secondary transformer neutral point is grounded in the interconnection transformer of this embodiment, but even in a system in which the neutral point is ungrounded or resistance grounded, if the transformer core is grounded, zero Since the phase current flows through the stray capacitance between the secondary winding and the iron core, the same effect is achieved.

  In this embodiment, the power converter 1 is connected to a permanent magnet generator. However, as shown in FIG. 14, instead of the generator, another power system (AC system) is connected via the interconnection transformer 30b. The same effect can be obtained with the power converter for power flow control that is connected to 3000 and controls the power flow between the power systems (AC systems) 1000 and 3000.

  In the present embodiment, the power converter 1 is connected to the permanent magnet generator, but the power converter 1 is connected to two transmission lines connected to the same substation 1000s as shown in FIG. A power conversion device for power transmission line current balancing that controls the power flow between the power transmission lines has the same effect.

  This embodiment will be described with reference to FIG. The difference between the present embodiment and the first embodiment is that the power converters 20 and 21 are changed to choppers 60 and 61. Only the differences from the first embodiment will be described. In FIG. 2, the same functional parts as those in FIG.

  The power converter 1 of the present embodiment is a solar inverter that converts the generated power of the solar panel into AC power and outputs the AC power to the AC system.

  The power converter 1 boosts DC power generated by the solar panels 90 and 91 by the choppers 60 and 61, converts the boosted DC power to AC power by the inverter 100, and converts the AC power via the interconnection transformer 30. Output power to the grid.

  A main circuit of the chopper 60 is shown in FIG. The chopper 60 includes an IGBT 60b, freewheeling diodes 60a and 60c, a DC smoothing capacitor 60d, and a boosting reactor 60e.

  The IGBT 60b is ON / OFF controlled by a gate signal output from the control device 1000. The step-up operation of the chopper 60 that realizes power transmission from a low-voltage solar panel to a high-voltage DC circuit will be briefly described.

  Since the solar panel 90 is short-circuited via the reactor 60e when the IGBT 60b is on, the current flowing through the reactor 60e increases. When the IGBT 60b is turned off, the current flowing through the reactor 60e flows into the DC circuit via the 60a.

  Since the voltage of the DC circuit is lower than the output voltage of the solar panel 90, the current of the reactor 60e attenuates while the IGBT 60b is off, but when the current is reduced to zero, the reactor 60e flows through the freewheeling diodes 60a and 60c. The current is clamped to zero.

  When the IGBT 60b is turned on again, the current flowing through the reactor 60e increases from zero, and when the IGBT 60b is turned off, current flows from the solar panel side to the DC circuit. The above is the boosting operation principle of the choppers 60 and 61.

  A solar panel of several kW or more is obtained by connecting several tens of panels in series or in parallel, and each panel is grounded to prevent electric shock. Therefore, the stray capacitances 901 and 911 from the power converter 1 to the expected ground are extremely large.

  Since the power output from the solar panel is direct current, the output voltage of the choppers 60 and 61 is direct current. On the other hand, the voltage output from the inverter 100 is alternating current. Therefore, the IGBT switching timings of the inverter 100 and the choppers 60 and 61 are different. Therefore, the zero phase current flows through the stray capacitance with respect to the ground of the solar panel as in the first embodiment.

  In the power converter 1 of the present embodiment, reactors (DC reactors) 51 to 58 are connected to the DC terminals of the inverters 10 and 11 and the DC terminals of the choppers 60 and 61, and the inverter 100 and the chopper 60, Since 61 is connected by a DC circuit, a zero-phase current flowing through the ground can be suppressed.

  Further, by selecting the inductance of the reactors 53, 54, 57, and 58 so that the resonance frequency determined by the chopper capacitor capacity and the inductance of the reactors 53, 54, 57, and 58 is lower than the chopper switching frequency, an excessive direct current oscillation current can be obtained. Can be avoided.

  In addition, as shown in FIG. 6, even when the solar panel is directly connected to the inverter 100 without using the step-up chopper, the DC circuit potential with respect to the ground fluctuates due to the switching of the inverter 100, so Current flows. Since the reactors (DC reactors) 51, 52, 53, and 54 of this embodiment can insert inductance into the zero-phase current circuit that flows through the stray capacitance 901, the same effects can be achieved.

  Further, as shown in FIG. 3, the power received from the system is converted into direct current by the inverter 100, the alternating voltage is supplied from the converter 200 to the load 5, and a power failure occurs in the alternating current system, the chopper 62 is used. Even in an uninterruptible power supply that supplies power from the storage battery 92 to the load 5, a zero-phase current flows through the inverter 100 and the chopper 62 through the inter-ground stray capacitances 921 and 931 of the storage battery. The same effect as that of the power converter 1 shown in FIG.

  Further, as shown in FIG. 9, fluctuations in the generated power of the wind farm 3000 are detected, and charging / discharging of the storage battery 92 via the power converter 1 is performed, thereby suppressing fluctuations in the AC generated power transmitted to the power system. The same power storage system as the power converter 1 shown in FIG.

  According to the present embodiment, it is possible to simultaneously suppress the oscillating current between the unit power converters and reduce the zero-phase current.

  Furthermore, even in a power conversion system that converts AC power into DC power, it is possible to reduce DC oscillation current and zero-phase current.

  That is, in the power converter of the present embodiment, by inserting the gapd reactor on the positive electrode side and the negative electrode side of the DC circuit, the circuit impedance through which the zero-phase current flows can be increased, the zero-phase current is reduced, and the DC circuit The current is reduced. Therefore, the temperature rise of the DC circuit and the temperature rise of the DC capacitor can be suppressed.

  Moreover, since the high frequency oscillating current flowing through the DC capacitor and the DC circuit can be suppressed by inserting the reactor into the DC circuit, the temperature rise of the DC capacitor can be suppressed.

  Furthermore, by providing the reactor with a gap, stray loss increases and attenuation of the oscillating current flowing through the LC circuit composed of the reactor and the DC capacitor can be promoted. The temperature rise of the DC capacitor can be suppressed.

1 Power converter 10, 11, 100 Inverter 20, 21, 200 Converter 40 Permanent magnet generator 51, 52, 53, 54, 55, 56, 57, 58, 500, 501 Reactor 60, 61, 62 Chopper 70 Shaft 80 Blades 90, 91 Solar panels 901, 911, 921, 931 Floating capacitance 1000 Controller 1000G1, 1000G2, 1000G3 Gate signal 3000 Wind farm 5102, 5105, 5106 Copper bar 5103, 5104 Insulator 5110 Wiring 5200, 5300 Non-magnetic material 6000 Case of power converter 1 10000, 30000 Power system 51011, 51012 Iron core

Claims (12)

A first power conversion unit that converts DC power applied to a first DC side terminal composed of a first positive DC terminal and a first negative DC terminal into AC power by a first semiconductor switching element; ,
A second DC switching terminal including a second positive DC terminal and a second negative DC terminal; and a second semiconductor switching element, wherein the second semiconductor switching element is AC power or DC A second power conversion unit that converts power to output to the second DC side terminal or converts DC power applied to the second DC side terminal to AC power; and
A capacitor for smoothing fluctuations associated with the switching operation of the first switching element or the second switching element;
The first positive DC terminal and the second positive DC terminal are connected via a reactor, and the first negative DC terminal and the second negative DC terminal are connected via a reactor. The power conversion system characterized by doing.   The power conversion system according to claim 1, wherein at least one of the reactors includes an iron core, and the iron core has a gap.   3. The power conversion system according to claim 2, wherein a gap between iron cores constituting at least one of the reactors is 0.5 mm or more.   4. The power conversion system according to claim 2, wherein at least one of the reactors is an outer iron type reactor. 5.   5. The power conversion system according to claim 2, further comprising means for fixing a potential of an iron core of a reactor connected to a positive electrode side of the reactor to a positive electrode of a DC circuit. Power conversion system.   5. The power conversion system according to claim 2, further comprising means for fixing a potential of an iron core of a reactor connected to a negative electrode side of the reactor to a negative electrode of a DC circuit. Power conversion system.   The power conversion system according to any one of claims 3 to 6, wherein a DC circuit current flows through a metal bar penetrating the iron core, and the metal bar is fixed to the housing via an insulator. Power conversion system.   The power conversion system according to any one of claims 1 to 7, wherein a resonance frequency of a series circuit of a reactor connected to a DC smoothing capacitor capacity and a DC circuit of the power converter is that of the power converter. A power conversion system characterized by being lower than a switching frequency.   The power conversion system according to any one of claims 1 to 8, wherein the power conversion system includes an AC output terminal, and the AC output terminal is connected to at least two different power sources via a harmonic filter reactor. Power conversion system characterized by being made.   The power conversion system according to claim 9, wherein one of the power sources is a generator grounded in a casing.   The power conversion system according to claim 9, wherein one of the power sources is a storage battery.   The power conversion system according to any one of claims 1 to 11, further comprising at least one AC system reactor, wherein the iron core of the reactor is a tripod iron core.

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