JP6521326B2 - AC-DC converter and control method thereof - Google Patents

Description

  Embodiments of the present invention relate to an AC-DC converter and a control method thereof.

  There is an AC / DC converter that converts DC power into AC power and supplies AC power after conversion to an AC power system. The AC-DC converter supplies unbalanced AC power to the power system when unbalance occurs in the AC power of the power system. Thus, the AC-DC converter suppresses unbalance of AC power of the power system and stabilizes AC power of the power system.

  The AC-DC converter has a converter in which a plurality of self-excited switching elements are bridge-connected. The AC / DC converter controls the operation of the converter, for example, by PWM (Pulse Width Modulation) control. In PWM control, a control signal of each switching element is generated by comparing a sinusoidal voltage command and a triangular carrier signal.

  In PWM control, a third harmonic having a frequency three times that of a sine wave voltage command is superimposed, and a carrier signal is compared with the voltage command after the superposition. Thereby, for example, the peak of the voltage command can be reduced, and the utilization rate of the DC voltage can be improved.

  However, in the case of outputting unbalanced AC power, when the third harmonic is superimposed as described above, the peak of the voltage command may be increased in the opposite direction. For this reason, in the AC-DC converter, it is desirable to suppress the peak of the voltage command and improve the utilization rate of the DC voltage even when outputting unbalanced AC power.

JP, 2008-193770, A

  An embodiment of the present invention provides an AC / DC converter capable of suppressing a peak of a voltage command even when outputting unbalanced AC power, and a control method thereof.

  According to an embodiment of the present invention, an AC / DC converter comprising a converter and a control circuit is provided. The converter has a plurality of bridge-connected self-excited switching elements, is connected to a DC circuit and a multiphase AC power system, and is supplied from the DC circuit by turning on / off the plurality of switching elements. DC power is converted into AC power of the polyphase AC, and the AC power is supplied to the power system. The control circuit generates a sinusoidal basic signal for each phase of the power system when an imbalance of the power system is detected, and superimposes a third harmonic on the basic signal for each phase to generate each phase. A plurality of control signals are generated for each of the plurality of switching elements, and the plurality of control signals are generated. The alternating current power of at least one of reactive power and reverse phase power according to the unbalance is supplied to the power system by controlling on / off of the plurality of switching elements by inputting to the switching element. The control circuit detects at least one of an amplitude and a phase angle for each of the base signals of each phase, and determines an amplitude and a phase angle of the third harmonic based on at least one of the detected amplitude and phase angle. Do.

  An AC / DC converter capable of suppressing a peak of a voltage command even when outputting unbalanced AC power, and a control method thereof are provided.

FIG. 1 is a block diagram schematically showing an AC-DC converter according to a first embodiment. FIG. 2A to FIG. 2D are graphs schematically showing an example of the operation of the control circuit according to the first embodiment. It is a block diagram showing the control circuit concerning a 1st embodiment typically. It is a block diagram which represents typically the third harmonic generation part which concerns on 1st Embodiment. It is a flowchart which represents operation | movement of the control circuit which concerns on 1st Embodiment typically. FIGS. 6A and 6B are graphs schematically showing an example of the basic signal and the voltage command signal. FIGS. 7A and 7B are graphs schematically showing an example of the basic signal and the voltage command signal. It is a block diagram which represents typically the third harmonic generation part which concerns on 2nd Embodiment. It is a block diagram which represents the 3rd harmonic generation part concerning a 3rd embodiment typically. It is a block diagram which represents the 3rd harmonic generation part concerning a 4th embodiment typically.

Hereinafter, each embodiment will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of sizes between parts, and the like are not necessarily the same as the actual ones. In addition, even in the case of representing the same portion, the dimensions and ratios may be different from one another depending on the drawings.
In the specification of the present application and the drawings, the same elements as those described above with reference to the drawings are denoted by the same reference numerals, and the detailed description will be appropriately omitted.

First Embodiment
FIG. 1 is a block diagram schematically showing an AC-DC converter according to a first embodiment.
As shown in FIG. 1, the AC-DC converter 10 includes a converter 12 and a control circuit 14. The converter 12 is connected to the power system 2 and the DC circuit 4.

  The power system 2 is a polyphase AC power system. The converter 12 is connected to the power system 2 via, for example, a transformer 5. Loads 6 a and 6 b are connected to the power system 2. The power system 2 supplies, for example, three-phase AC power to the loads 6a and 6b. The AC power of the power system 2 is not limited to three phases, and may be two phases or four or more phases. Below, the alternating current power of the electric power grid | system 2 is demonstrated as three-phase alternating current power.

  The DC circuit 4 is, for example, a storage device such as a capacitor. The DC circuit 4 may be, for example, a converter that converts AC power supplied from a power system different from the power system 2 into DC power. The DC circuit 4 may be any circuit capable of supplying DC power to the converter 12.

  The AC-DC converter 10 supplies reactive power and reverse-phase power to the power system 2 based on the DC power of the DC circuit 4 when unbalance occurs in the AC power of the power system 2. In the AC / DC converter 10, the reactive power and the reverse phase power are transmitted to the power system 2 so that the active power of each phase of the power system 2 becomes substantially the same and the reactive power of each phase becomes substantially zero. Output to Thus, the AC / DC converter 10 performs reactive power compensation and reverse phase power compensation of the AC power of the power system 2 to stabilize the AC power of the power system 2. The AC power output from the AC / DC converter 10 may be at least one of reactive power and reverse phase power.

  The AC / DC conversion device 10 is used, for example, in a transmission system of an electric railway. In the transmission system of the electric railway, Scott Transformer 7 is connected to power system 2, the three-phase AC power of power system 2 is converted to two single-phase AC powers, and each single-phase AC power is converted by loads 6a and 6b. It is done to supply to a certain rail car. In this case, unbalance occurs in the three-phase AC power of the electric power system 2 depending on the operating condition of each railcar. For example, in the transmission system of the electric railway, the AC / DC converter 10 is connected to the power system 2 in the vicinity of the Scott transformer 7. Thereby, the unbalance of the electric power which arises in the electric power grid | system 2 by driving | operation of a rail vehicle can be suppressed.

  When DC circuit 4 is a power storage device, for example, when AC power of power system 2 is in a steady state, AC power of power system 2 is converted into DC power corresponding to DC circuit 4. , DC power is supplied to the DC circuit 4. That is, the AC-DC converter 10 charges the DC circuit 4 based on the AC power of the power system 2.

  The converter 12 has a plurality of switching elements 20 u, 20 v, 20 w, 20 x, 20 y, 20 z, and a plurality of rectifying elements 21 u, 21 v, 21 w, 21 x, 21 y, 21 z. Hereinafter, when the switching elements 20 u, 20 v, 20 w, 20 x, 20 y, and 20 z are collectively referred to, they are referred to as “each switching element 20”. When each of the rectifying elements 21 u, 21 v, 21 w, 21 x, 21 y, 21 z is collectively referred to as “each rectifying element 21”.

  Each switching element 20 is bridged. In this example, six switching elements 20 corresponding to the three-phase AC power of power system 2 are provided in converter 12. That is, converter 12 is a so-called three-phase inverter. The converter 12 performs conversion of DC power to AC power and conversion of AC power to DC power by turning on / off each switching element 20. For each switching element 20, for example, a self-excited switching element (self-arc extinguishing element) such as IGBT (Insulated Gate Bipolar Transistor) or GTO (Gate Turn-Off thyristor) is used.

  Below, when expressing three phases of three-phase alternating current power of electric power system 2 separately and expressing, it explains as U phase, V phase, and W phase. In converter 12, switching elements 20u and 20x correspond to the U phase, switching elements 20v and 20y correspond to the V phase, and switching elements 20w and 20z correspond to the W phase. The switching elements 20 u, 20 v, 20 w are upper arms of the respective phases, and the switching elements 20 x, 20 y, 20 z are lower arms of the respective phases.

  Each rectifying element 21 is connected in antiparallel to each switching element 20. For each rectifying element 21, for example, a diode is used. Each rectifying element 21 is a so-called reflux diode. The number of switching elements 20 and the number of rectifying elements 21 are not limited to six, and may be any number corresponding to the number of AC power phases of power system 2.

  The control circuit 14 is connected to a control terminal (for example, a gate terminal) of each switching element 20. The control circuit 14 controls the on / off of each switching element 20 by inputting a control signal (gate signal) to the control terminal of each switching element 20. Thus, the control circuit 14 controls the conversion of power by the converter 12.

  The AC-DC converter 10 further includes current detectors 16u, 16v, 16w, voltage detectors 17u, 17v, 17w, and current detectors 18u, 18v, 18w. Each of the current detectors 16 u, 16 v, 16 w detects the output current of each phase of the AC power output from the converter 12, and inputs the detection result to the control circuit 14. The voltage detectors 17 u, 17 v and 17 w detect line voltages of respective phases of the power system 2 and input detection results to the control circuit 14. Each of the current detectors 18 u, 18 v, 18 w detects the load current of each phase of the power system 2 and inputs the detection result to the control circuit 14. The control circuit 14 controls on / off of each switching element 20 based on each detection result of the input current and voltage.

FIG. 2A to FIG. 2D are graphs schematically showing an example of the operation of the control circuit according to the first embodiment.
FIGS. 2A to 2D show an example of a generation procedure of control signals of the switching elements 20 by the control circuit 14.
In FIG. 2A to FIG. 2D, the procedure of generating the control signal of each of the U-phase switchings 20u and 20x is represented for convenience.

  When the control circuit 14 generates control signals for the switching elements 20u and 20x, first, as shown in FIG. 2A, the control circuit 14 generates a sinusoidal base signal BSu. The control circuit 14 obtains the phase voltage of the U phase from, for example, the detection result of the voltage detector 17 u. A voltage command value of each phase of three-phase AC power of the power system 2 is input to the control circuit 14. For example, the control circuit 14 obtains a difference between the phase voltage and the voltage command value, and performs a proportional integral operation on this difference. Thereby, the control circuit 14 generates the basic signal BSu for bringing the phase voltage of the U phase of the AC power output from the converter 12 close to the voltage command value.

  The control circuit 14 generates a third harmonic TH having a frequency that is three times the frequency of the fundamental wave of the AC power of the power system 2. Then, the control circuit 14 generates the voltage command signal Vuref of the U phase as shown in FIG. 2B by superposing the third harmonic TH on the basic signal BSu.

  Further, as shown in FIG. 2B, the control circuit 14 generates a triangular carrier signal CS. The frequency of the carrier signal CS is higher than the frequency of the AC power fundamental wave of the power system 2. The amplitude of the carrier signal CS is set to, for example, substantially the same as the amplitude of the fundamental wave of the AC power of the power system 2.

  The control circuit 14 compares the carrier signal CS with the voltage command signal Vuref to generate a control signal Sgu of the switching element 20u, which is the upper arm of the U phase, as shown in FIG. 2C. The control circuit 14 generates the control signal Sgu such that the switching element 20u is turned on when the voltage command signal Vuref is higher than the carrier signal CS.

  Then, as illustrated in FIG. 2D, the control circuit 14 generates a control signal Sgx of the switching element 20x that is the lower arm of the U phase by inverting the control signal Sgu.

  The control circuit 14 generates control signals for the V-phase and W-phase switching elements 20 by performing the same process as described above for the V-phase and the W-phase. The control circuit 14 inputs each generated control signal to the control terminal of each switching element 20. Thereby, the control circuit 14 controls on / off of each switching element 20.

  Thus, the control circuit 14 controls on / off of each switching element 20 by so-called PWM (Pulse Width Modulation) control. At this time, the control circuit 14 generates a voltage command signal Vuref by superimposing the third harmonic TH on the basic signal BSu. Thus, the maximum value of the fundamental wave component of the output voltage can be increased, and the voltage utilization factor of the inverter can be improved.

  For example, when the control signal is generated by comparing the carrier signal CS and the sinusoidal base signal BSu, the amplitude of the fundamental wave of the output voltage is limited to √3 / 2 or less of the DC voltage. As described above, the amplitude of the fundamental wave of the output voltage can be made larger than √3 / 2 of the DC voltage by superimposing the third harmonic TH. For example, the third harmonic TH having an amplitude of 1⁄6 of the amplitude of the base signal BSu is superimposed. Thereby, the peak value of the basic signal BSu can be minimized, and the amplitude of the fundamental wave of the output voltage can be made larger than √3 / 2 of the DC voltage.

  The carrier signal CS and the third harmonic TH are commonly used to generate control signals of respective phases. The carrier signal CS may be prepared, for example, for each phase.

FIG. 3 is a block diagram schematically showing the control circuit according to the first embodiment.
FIG. 3 is a block diagram schematically showing a configuration of a generation portion of voltage command signals Vuref, Vvref, Vwref of control circuit 14. In FIG.
As shown in FIG. 3, the control circuit 14 has a basic signal generation unit 30, an amplitude phase angle detection unit 32, a third harmonic generation unit 34, and adders 36u, 36v, 36w.

  The detection values Vdetu, Vdetv, Vdetw of the voltage detectors 17 u, 17 v, 17 w are input to the basic signal generation unit 30. The basic signal generation unit 30 generates the basic signals BSu, BSv, and BSw of the respective phases of the AC power output from the converter 12 based on the detection values Vdetu, Vdetv, and Vdetw as described above. The basic signal generation unit 30 inputs the generated basic signals BSu, BSv, and BSw to the amplitude and phase angle detection unit 32 and the adders 36u, 36v, and 36w.

  The amplitude phase angle detection unit 32 detects the amplitudes Vu, Vv, Vw of the respective input basic signals BSu, BSv, BSw, and also detects the phase angles φu, φv, of the respective basic signals BSu, BSv, BSw. Detect φw. The amplitude phase angle detection unit 32 inputs the detected amplitudes Vu, Vv, Vw and the phase angles φu, φv, φw to the third harmonic generation unit 34.

  The phase angles φu, φv, φw are, in other words, the phase differences of the basic signals BSu, BSv, BSw with respect to the reference phase θ of the AC voltage of the power system 2. The reference phase θ is, for example, the phase of the U phase of the power system 2. In this case, the optimum value of the phase angle φu is 0 °. The optimum value of the phase angle φv is 120 °. The optimum value of the phase angle φw is 240 °.

  The detected values of the amplitude and the phase angle are input to the third harmonic generation unit 34, and the reference phase θ is input. The third harmonic generation unit 34 generates the amplitude k of the third harmonic TH and the phase of the third harmonic TH based on the input reference phase θ, each amplitude Vu, Vv, Vw and each phase angle φu, φv, φw. Find the angle φm. The third harmonic generation unit 34 generates the third harmonic TH based on the equation of k × sin (3θ + φm) from the determined amplitude k and phase angle φm. Then, the third harmonic generation unit 34 inputs the generated third harmonic TH to the adders 36 u, 36 v, and 36 w.

  The adder 36u adds the third harmonic TH to the input basic signal BSu. That is, the adder 36 u generates the voltage command signal Vuref of the U phase from the basic signal BSu and the third harmonic TH by superimposing the third harmonic TH on the basic signal BSu. Similarly, the adder 36v generates a voltage command signal Vvref of V phase by superimposing the third harmonic TH on the basic signal BSv. The adder 36 w generates a W-phase voltage command signal Vwref by superimposing the third harmonic TH on the basic signal BSw.

FIG. 4 is a block diagram schematically showing a third harmonic generation unit according to the first embodiment.
As shown in FIG. 4, the third harmonic generation unit 34 includes an amplitude phase angle determination unit 40 and a generation unit 42. The amplitude phase angle determination unit 40 has table data 44. In the table data 44, the amplitudes Vu, Vv, Vw and phase angles φu, φv, φw of the basic signals BSu, BSv, BSw, and the amplitude k and phase angle φm of the third harmonic TH are associated.

  More specifically, in the table data 44, the peak value of the voltage command signal Vuref, the peak value of the voltage command signal Vvref, and the amplitudes Vu, Vv, Vw and the phase angles φu, φv, φw, and The amplitude k and the phase angle φm at which the maximum value of the peak value of the voltage command signal Vwref is minimized are associated. Thus, the table data 44 stores the combination of the amplitude k and the phase angle φm for minimizing the highest value of the three peak values of the voltage command signal of each phase.

  The amplitude phase angle determination unit 40 receives the amplitudes Vu, Vv, Vw and the phase angles φu, φv, φw. The amplitude phase angle determination unit 40 refers to the table data 44 based on the input amplitudes Vu, Vv, Vw and the phase angles φu, φv, φw. Thereby, amplitude phase angle determination unit 40 sets amplitude k and phase angle φm at which the peak value of voltage command signal Vuref, the peak value of voltage command signal Vvref, and the maximum value of the peak value of voltage command signal Vwref are minimized. It reads from the table data 44.

  The amplitude phase angle determination unit 40 determines the value read from the table data 44 as the amplitude k and the phase angle φm of the third harmonic TH, and inputs the determined amplitude k and the phase angle φm to the generation unit 42.

  As described above, the amplitude phase angle determination unit 40 determines the peak value of Vu × sin (θ + φu) + k × sin (3θ + φm), the peak value of Vv × sin (θ + φv) + k × sin (3θ + φm), and Vw × sin ( The amplitude k and the phase angle φm at which the maximum value of the peak value of θ + φw) + k × sin (3θ + φm) becomes minimum are determined.

  For example, the potential difference between the amplitude Vu of the base signal BSu and the amplitude Vv of the base signal BSv, the potential difference between the amplitude Vu of the base signal BSu and the amplitude Vw of the base signal BSw, and the base signal BSu Table data by correlating the phase difference between the phase angle φu and the phase angle φv of the base signal BSv, the phase difference between the phase angle φu of the base signal BSu and the phase angle φw of the base signal BSw, the amplitude k and the phase angle φm Make it memorize in 44. Then, the amplitude k and the phase angle φm are read out from each potential difference and each phase difference. Thereby, the six variables of the amplitudes Vu, Vv, Vw and the phase angles φu, φv, φw can be reduced to four variables of the potential differences and the phase differences. Thereby, for example, it is possible to shorten the operation processing time for reading out the amplitude k and the phase angle φm.

  The generation unit 42 receives the amplitude k and the phase angle φm, and receives the reference phase θ. The generation unit 42 generates the third harmonic TH based on the equation k × sin (3θ + φm), and inputs the third harmonic TH to the adders 36 u, 36 v, and 36 w.

  FIG. 5 is a flow chart schematically showing the operation of the control circuit according to the first embodiment. As shown in FIG. 5, the control circuit 14 is based on the detection results of each of the current detectors 16u, 16v, 16w, each of the voltage detectors 17u, 17v, 17w, and each of the current detectors 18u, 18v, 18w. Then, the unbalance of the AC power of the power system 2 is detected (step S01 in FIG. 5). The control circuit 14 detects, for example, each of the unbalance of the amplitude and phase angle of the alternating current voltage of the power system 2 and the amplitude and phase angle of the alternating current.

  In this example, the control circuit 14 detects unbalance of AC power of the power system 2. Without being limited thereto, for example, an imbalance is detected in an external device such as a host controller of the AC / DC conversion device 10, and the detection of the imbalance is recognized in the control circuit 14 based on the information input from the external device. You may make it

  When the control circuit 14 detects an unbalance, the base signals BSu, BSv of each phase of the AC power output from the converter 12 based on the detection values Vdetu, Vdetv, Vdetw of the voltage detectors 17u, 17v, 17w. , BSw (step S02 in FIG. 5).

  The control circuit 14 detects the amplitudes Vu, Vv, Vw and the phase angles φu, φv, φw of the basic signals BSu, BSv, BSw after generating the basic signals BSu, BSv, BSw (FIG. 5). Step S03).

  The control circuit 14 determines the amplitude k and the phase angle φm of the third harmonic TH based on the amplitudes Vu, Vv and Vw of the detected basic signals BSu, BSv and BSw and the phase angles φu, φv and φw. (Step S04 in FIG. 5). The control circuit 14 determines the amplitude k and the phase angle φm of the third harmonic TH by reading out from the table data 44 in the amplitude phase angle determination unit 40, for example.

  In this example, the amplitude k and the phase angle φm of the third harmonic TH are determined based on the amplitudes Vu, Vv, Vw and the phase angles φu, φv, φw, respectively. Without being limited thereto, the amplitude k and the phase angle φm of the third harmonic TH may be determined based on at least one of the amplitudes Vu, Vv, Vw and the phase angles φu, φv, φw.

  The control circuit 14 generates a third harmonic TH based on the determined amplitude k and phase angle φm (step S05 in FIG. 5).

  After generating the third harmonics TH, the control circuit 14 superimposes the third harmonics TH on each of the basic signals BSu, BSv, and BSw to generate voltage command signals Vuref, Vvref, and Vwref of the respective phases (see FIG. Step S06 in FIG.

  The control circuit 14 generates control signals of the respective switching elements 20 by comparing the voltage command signals Vuref, Vvref, Vwref with the carrier signal CS (step S07 in FIG. 5).

  Then, the control circuit 14 controls the on / off of each switching element 20 by inputting each generated control signal to the control terminal of each switching element 20 (step S08 in FIG. 5). That is, the control circuit 14 controls the conversion from direct current power to alternating current power by the converter 12. As a result, the control circuit 14 supplies unbalance AC power of at least one of reactive power and reverse phase power according to the unbalance of the power system 2 from the converter 12 to unbalance the AC power of the power system 2. Suppress.

  Thus, the AC-DC converter 10 supplies imbalanced AC power to the power system 2 when imbalance occurs in AC power of the power system 2, thereby achieving unbalance of AC power of the power system 2. Suppress and stabilize the power system 2.

FIGS. 6A and 6B are graphs schematically showing an example of the basic signal and the voltage command signal.
FIG. 6A shows an example of the fundamental signals BSu, BSv, BSw and the third harmonic TH of each phase.
FIG. 6B shows an example of voltage command signals Vuref, Vvref, Vwref of each phase and a carrier signal CS.
6 (a) and 6 (b) illustrate the case where the AC power of the power system 2 is unbalanced. 6A and 6B show a reference example in which the amplitude k and the phase angle φm of the third harmonic TH are not adjusted but are set to predetermined values.

  As shown in FIGS. 6 (a) and 6 (b), when a constant third-order harmonic TH is superimposed on each of the fundamental signals BSu, BSv, and BSw in which an imbalance occurs, a voltage command signal Large peaks may occur in Vuref, Vvref, and Vwref. In this example, the peak of the voltage command signal Vvref is large. For example, when the peak of the voltage command signal Vvref becomes larger than the amplitude of the carrier signal CS, the controllability of the output voltage is reduced, and the harmonic component is increased.

FIGS. 7A and 7B are graphs schematically showing an example of the basic signal and the voltage command signal.
In FIGS. 7A and 7B, an example in which the third harmonics TH whose amplitude k and phase angle φm are adjusted are superimposed on the same basic signals BSu, BSv, and BSw as in FIG. 6A. It represents.

  As shown in FIGS. 7A and 7B, by adjusting the amplitude k and phase angle φm of the third harmonic TH, for example, the peak value of the voltage command signal Vuref, the peak of the voltage command signal Vvref The value and the maximum value of the peak value of the voltage command signal Vwref can be minimized. In this example, the peak value of the voltage command signal Vvref can be lowered. For example, the peak value of the voltage command signal Vvref can be made lower than the amplitude of the carrier signal CS.

  Thus, in the AC / DC converter 10 according to the present embodiment, the amplitude and phase angle of the third harmonic TH are adjusted in accordance with the amplitudes and phase angles of the basic signals BSu, BSv, and BSw. Thus, even when unbalanced AC power is output, the peaks of the voltage command signals Vuref, Vvref, and Vwref can be suppressed. For example, the utilization rate of DC voltage can be improved. The harmonic component of the output voltage can be suppressed.

Second Embodiment
FIG. 8 is a block diagram schematically showing a third harmonic generation unit according to the second embodiment.
As shown in FIG. 8, the third harmonic generation unit 34 includes a maximum value selection unit 50, a contact switching unit 51, contacts 52u, 52v, 52w, a coefficient circuit 53, and a generation unit 54. The same reference numerals are given to components substantially the same in function and configuration as the first embodiment, and the detailed description will be omitted.

  The amplitudes Vu, Vv, and Vw of the basic signals BSu, BSv, and BSw are input to the maximum value selection unit 50, respectively. The maximum value selection unit 50 selects the maximum value of each of the amplitudes Vu, Vv, and Vw, and inputs the maximum value to the contact switching unit 51 and the coefficient circuit 53.

  The contact switching unit 51 receives the maximum value selected by the maximum value selection unit 50 and also receives the amplitudes Vu, Vv, and Vw. The contact switching unit 51 is connected to control terminals of the contacts 52 u, 52 v, 52 w. The contact switching unit 51 switches on / off of the contacts 52 u, 52 v, 52 w based on the input amplitude value and maximum value.

  The phase angle φu of the U-phase base signal BSu is input to the contact 52u. The phase angle φv of the V-phase base signal BSv is input to the contact 52v. The phase angle φw of the W-phase basic signal BSw is input to the contact 52w. Each contact 52 u, 52 v, 52 w is connected to the generation unit 54. Therefore, one of the phase angles φu, φv, and φw is selectively input to the generation unit 54 by turning on and off the contacts 52u, 52v, and 52w.

  The contact switching unit 51 compares the amplitude Vu with the maximum value, and turns on the contact 52u when the amplitude Vu is the same as the maximum value. Similarly, the contact switching unit 51 compares the amplitude Vv with the maximum value, and turns on the contact 52v when the amplitude Vv is the same as the maximum value, and compares the amplitude Vw with the maximum value to obtain the amplitude Vw. And the maximum value is the same, the contact 52w is turned on. Thereby, the contact switching unit 51 inputs the phase angle of the phase with the largest amplitude Vu, Vv, and Vw to the generation unit 54 as the phase angle φm of the third harmonic TH.

  The coefficient circuit 53 multiplies the input maximum value by a predetermined coefficient, and inputs the maximum value obtained by multiplying the coefficient to the generation unit 54 as the amplitude k of the third harmonic TH. The coefficient multiplied by the coefficient circuit 53 is, for example, 1/6.

  The generation unit 54 generates the third harmonic TH based on the equation of k × sin (3θ + φm) based on the input amplitude k and phase angle φm, as in the first embodiment. Then, the generation unit 54 inputs the generated third harmonic TH to each of the adders 36u, 36v, and 36w.

  Thus, in this example, the third harmonic TH is generated in accordance with the fundamental signal of the phase with the largest amplitude. Also in this case, the peaks of the voltage command signals Vuref, Vvref, and Vwref can be suppressed. Further, in this case, the third harmonic TH can be easily generated as compared with the first embodiment. The processing load of the generation of the third harmonic TH in the control circuit 14 can be reduced.

  On the other hand, as in the first embodiment, the third order harmonic TH is set such that the peak value of the voltage command signal Vuref, the peak value of the voltage command signal Vvref, and the maximum value of the peak value of the voltage command signal Vwref are minimized. When the voltage command signals Vuref, Vvref and Vwref are generated, the peaks of the voltage command signals Vuref, Vvref and Vwref can be suppressed more appropriately.

Third Embodiment
FIG. 9 is a block diagram schematically showing a third harmonic generation unit according to the third embodiment.
As shown in FIG. 9, the third harmonic generation unit 34 includes the contacts 60u, 60v, 60w, the coefficient circuit 61, the subtracters 62, 63, the absolute value circuit 64, the minimum value selection unit 65, the contact switching. And a generation unit 67.

  The amplitude Vu of the basic signal BSu is input to the contact point 60u. The amplitude Vv of the basic signal BSv is input to the contact 60v. The amplitude Vw of the basic signal BSw is input to the contact point 60w. Each contact 60 u, 60 v, 60 w is connected to the coefficient circuit 61. Thereby, any one of the amplitudes Vu, Vv and Vw is selectively input to the coefficient circuit 61 by turning on and off each of the contacts 60u, 60v and 60w.

  The subtractor 62 receives the phase angle φv of the V-phase base signal BSv. Further, a reference value of the phase angle φv is input to the subtractor 62. In this example, 120 ° is input to the subtractor 62 as a reference value of the phase angle φv. The subtracter 62 calculates the difference between the phase angle φv and the reference value, and inputs the calculated difference to the absolute value circuit 64.

  The subtractor 63 receives the phase angle φw of the W-phase basic signal BSw. Further, a reference value of the phase angle φw is input to the subtractor 63. In this example, 240 ° is input to the subtractor 63 as a reference value of the phase angle φw. The subtractor 63 calculates the difference between the phase angle φw and the reference value, and inputs the calculated difference to the absolute value circuit 64.

  The absolute value circuit 64 receives the difference calculated by each of the subtractors 62 and 63, and also receives the phase angle φu of the U-phase base signal BSu. The absolute value circuit 64 obtains the absolute value of each input value, and inputs each absolute value to the minimum value selection unit 65 and the contact switching unit 66. That is, the absolute value circuit 64 inputs the absolute value of the difference between each phase angle φu, φv, φw to the reference value to the minimum value selection unit 65 and the contact point switching unit 66.

  The minimum value selection unit 65 selects the minimum value of the absolute values of the differences from the reference values of the phase angles φu, φv, and φw, and inputs the minimum value to the contact switching unit 66. Further, the minimum value selection unit 65 inputs the selected minimum value to the generation unit 67 as the phase angle φm of the third harmonic TH.

  The contact switching unit 66 is connected to control terminals of the contacts 60 u, 60 v, 60 w. The contact switching unit 66 switches on / off of the contacts 60 u, 60 v, and 60 w based on the input absolute value and minimum value.

  The contact switching unit 66 compares the absolute value and the minimum value of the phase angle φu, and turns on the contact 60 u when the absolute value and the minimum value are the same. Similarly, contact switching unit 66 compares the absolute value and the minimum value of the difference between the phase angle φ v and the reference value, and turns on contact 60 v when the absolute value and the minimum value are the same, and the phase angle The absolute value and the minimum value of the difference from the reference value of φw are compared, and if the absolute value and the minimum value are the same, the contact point 60w is turned on. Thereby, the contact point switching unit 66 inputs the amplitude of the phase having the smallest absolute value of the difference between each of the phase angles φu, φv, φw and the reference value to the coefficient circuit 61.

  The coefficient circuit 61 multiplies the input amplitude by a predetermined coefficient, and inputs the amplitude after the coefficient to the generation unit 67 as the amplitude k of the third harmonic TH. The coefficient multiplied by the coefficient circuit 61 is, for example, 1/6.

  The generation unit 67 generates the third harmonic TH based on the equation of k × sin (3θ + φm) based on the input amplitude k and phase angle φm. Then, the generation unit 67 inputs the generated third harmonic TH to each of the adders 36u, 36v, and 36w.

  As described above, in this example, the third harmonic TH is generated in accordance with the basic signal of the phase having the smallest absolute value of the difference between each of the phase angles φu, φv, φw and the reference value. Also in this case, the peaks of the voltage command signals Vuref, Vvref, and Vwref can be suppressed. In this case, the third harmonic TH can be easily generated as compared with the first embodiment. The processing load of the generation of the third harmonic TH in the control circuit 14 can be reduced.

Fourth Embodiment
FIG. 10 is a block diagram schematically showing a third harmonic generation unit according to the fourth embodiment.
As shown in FIG. 10, the third harmonic generation unit 34 includes subtractors 70 and 71, average value circuits 72 and 73, a coefficient circuit 74, and a generation unit 75.

  The subtractor 70 receives the phase angle φv of the V-phase base signal BSv and the reference value of the phase angle φv. In this example, 120 ° is input to the subtractor 70 as a reference value of the phase angle φv. Subtractor 70 calculates the difference between phase angle φ v and the reference value, and inputs the calculated difference to average value circuit 73.

  The subtractor 71 receives the phase angle φw of the W-phase basic signal BSw and the reference value of the phase angle φw. In this example, 240 ° is input to the subtractor 71 as a reference value of the phase angle φw. The subtractor 71 calculates the difference between the phase angle φw and the reference value, and inputs the calculated difference to the average value circuit 73.

  The amplitudes Vu, Vv, and Vw of the basic signals BSu, BSv, and BSw are input to the average value circuit 72, respectively. The average value circuit 72 calculates an average value of the amplitudes Vu, Vv and Vw, and inputs the calculated average value to the coefficient circuit 74.

  The average value circuit 73 receives the difference calculated by each of the subtractors 70 and 71, and also receives the phase angle φu of the U-phase base signal BSu. The average value circuit 73 obtains an average value of each input value. That is, the average value circuit 73 obtains the average value of the differences between the phase angles φu, φv, and φw with the reference values. The average value circuit 73 inputs the calculated average value to the generation unit 75 as the phase angle φm of the third harmonic TH.

  The coefficient circuit 74 multiplies the average value of the input amplitudes by a predetermined coefficient, and inputs the amplitude after the coefficients to the generation unit 75 as the amplitude k of the third harmonic TH. The coefficient multiplied by the coefficient circuit 75 is, for example, 1/6.

  The generation unit 75 generates the third harmonic TH based on the equation of k × sin (3θ + φm) based on the input amplitude k and phase angle φm. Then, the generation unit 75 inputs the generated third harmonic TH to each of the adders 36u, 36v, and 36w.

  As described above, in this example, the third harmonic TH is generated based on the average value of each of the amplitudes Vu, Vv, and Vw and the average value of the difference between each of the phase angles φu, φv, and φw and the reference value. Also in this case, the peaks of the voltage command signals Vuref, Vvref, and Vwref can be suppressed. In this case, the third harmonic TH can be easily generated as compared with the first embodiment. The processing load of the generation of the third harmonic TH in the control circuit 14 can be reduced.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 2 ... Power system, 4 ... DC circuit, 5 ... Transformer, 6a, 6b ... Load, 7 ... Scott transformer, 10 ... AC / DC conversion device, 12 ... Converter, 14 ... Control circuit, 16u, 16v, 16w ... Current detection , 17u, 17v, 17w ... voltage detector, 18u, 18v, 18w ... current detector, 20, 20u, 20v, 20w, 20x, 20y, 20z ... switching elements 21, 21u, 21v, 21w, 21x, 21y , 21z: rectification element, 30: basic signal generation unit, 32: amplitude phase angle detection unit, 34: third order harmonic generation unit, 36u, 36v, 36w ... adder, 40: amplitude phase angle determination unit, 42: generation unit 44 Table data 50 Maximum value selection unit 51 Contact switching unit 52u, 52v, 52w Contact point 53 Coefficient circuit 54 Generation unit 0u, 60v, 60w ... contact point, 61 ... coefficient circuit, 62, 63 ... subtractor, 64 ... absolute value circuit, 65 ... minimum value selection unit, 66 ... contact switching unit, 67 ... generation unit, 70, 71 ... subtractor , 72, 73 ... average value circuit, 74 ... coefficient circuit, 75 ... generation unit

Claims (5)

It has a plurality of bridge-connected self-excited switching elements, is connected to a DC circuit and a multiphase AC power system, and DC power supplied from the DC circuit is switched by turning on / off the plurality of switching elements. A converter for converting into multi-phase alternating current power and supplying the alternating current power to the power system;
When unbalance of the power system is detected, a sinusoidal basic signal is generated for each phase of the power system, and a third order harmonic is superimposed on the basic signal for each phase to generate a voltage command signal for each phase. Generating a plurality of control signals for each of the plurality of switching elements by comparing the voltage command signal for each phase with the carrier signal in a triangular wave shape, and inputting the plurality of control signals to the plurality of switching elements A control circuit which supplies the AC power of at least one of reactive power and reverse phase power according to the imbalance to the power system by controlling on / off of the plurality of switching elements;
Equipped with
The control circuit detects at least one of an amplitude and a phase angle for each of the base signals of each phase, and determines an amplitude and a phase angle of the third harmonic based on at least one of the detected amplitude and phase angle. AC-to-DC converter.   The control circuit includes table data in which the amplitudes and phase angles of the basic signals of the phases are associated with the amplitudes and phase angles of the third harmonics, and The AC / DC conversion device according to claim 1, wherein the amplitude and phase angle of the third harmonic are determined by reading out the amplitude and phase angle of the third harmonic from which the maximum value of each peak value is minimum from the table data.   The control circuit determines, as the amplitude of the third harmonic, a coefficient multiple of the maximum value of the amplitude of each of the basic signals of each phase, and the phase angle of the fundamental signal of the phase having the maximum amplitude is the third harmonic The AC / DC converter according to claim 1, wherein the AC / DC converter is determined as a phase angle of   The control circuit determines, as the amplitude of the third harmonic, a coefficient multiple of the average value of the amplitudes of the base signals of each phase as the amplitude of the third harmonic, and the difference with the reference value of the phase angle of each base signal of the phases. The AC / DC converter according to claim 1, wherein an average value is determined as a phase angle of the third harmonic. It has a plurality of bridge-connected self-excited switching elements, is connected to a DC circuit and a multiphase AC power system, and DC power supplied from the DC circuit is switched by turning on / off the plurality of switching elements. A converter for converting into multi-phase alternating current power and supplying the alternating current power to the power system;
When unbalance of the power system is detected, a sinusoidal basic signal is generated for each phase of the power system, and a third order harmonic is superimposed on the basic signal for each phase to generate a voltage command signal for each phase. Generating a plurality of control signals for each of the plurality of switching elements by comparing the voltage command signal for each phase with the carrier signal in a triangular wave shape, and inputting the plurality of control signals to the plurality of switching elements A control circuit which supplies the AC power of at least one of reactive power and reverse phase power according to the imbalance to the power system by controlling on / off of the plurality of switching elements;
Method of controlling an AC / DC converter comprising:
Detecting at least one of an amplitude and a phase angle for each of the base signals of each phase;
Determining the amplitude and phase angle of the third harmonic based on at least one of the detected amplitude and phase angle;
Method of controlling an AC / DC converter comprising:

Images