JP2007280358A - Self-excited reactive power compensation apparatus, capacitor voltage control method for self-excited reactive power compensation apparatus, power storage apparatus, and power storage apparatus control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a self-excited reactive power compensation apparatus comprising a plurality of single phase power converters cascaded on an AC side, and a capacitor voltage control method therefor that can stably control DC voltage values of capacitors connected to a DC side of the single phase power converters, respectively. <P>SOLUTION: The self-excited reactive power compensation apparatus 1 comprises an arithmetic means 11 for calculating a DC voltage average of all the capacitors disposed on the DC side of the single phase power converters, a first DC capacitor voltage control means 12 for generating a first switching command value for matching the DC voltage average to a command value, and second DC capacitor voltage control means 13-1 to 13-3 each for generating a second switching command value for matching the respective DC voltage value to the DC voltage average. Switching control in each single phase power converter based on the first switching command value and second switching command value controls the respective capacitor voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is configured such that the AC sides of a plurality of single-phase power converters are cascade-connected to each other, and a capacitor connected to the DC side of each single-phase power converter is used as a DC voltage source to generate reactive power. The present invention relates to an excited reactive power compensator, a capacitor voltage control method in the self-excited reactive power compensator, and a power storage device and a power storage device control method for leveling short-period fluctuations in power.

  In a distribution system connected with a lot of inductive loads, a delay power factor results, so that reactive power flows through the distribution system and the system voltage becomes unstable. In addition, it is expected that the introduction of distributed power sources will be actively promoted in various forms in the future, and voltage fluctuations in the distribution system accompanying this can be a major problem. On the other hand, a reactive power compensator has been proposed as a measure for improving the stability and power factor of the distribution system. Of these, the self-excited reactive power compensator (STATCOM) has the advantage that continuous reactive power control from the slow phase to the true phase is possible and that harmonics are not easily generated.

  The self-excited reactive power compensator includes a reactor connected to the AC side thereof and a single-phase power converter such as a single-phase full-bridge (full-wave) voltage type PWM converter. A capacitor is connected to the DC side of the single-phase power converter, and the self-excited reactive power compensator uses this capacitor as a DC voltage source to generate reactive power.

  When the self-excited reactive power compensator is connected to a distribution system (for example, 6.6 kV system) via a commercial frequency transformer (50/60 Hz), the weight of the commercial frequency transformer connected to the self-excited reactive power compensator and The volume must be large. In particular, a self-excited reactive power compensator for a distribution system is required to be reduced in size and weight because it is installed on a pillar. Under such circumstances, development of a transformerless self-excited reactive power compensator that does not require the use of a commercial frequency transformer is particularly desired.

  As a transformerless self-excited reactive power compensator, a single-phase power converter (for example, a single-phase full-bridge voltage type PWM converter) is configured by cascading (cascading) a plurality of units (hereinafter simply referred to as “cascade connection type”). (Refer to non-patent document 1, for example). FIG. 15 is a circuit configuration diagram illustrating a general cascade connection type (Y connection) three-phase self-excited reactive power compensator.

The cascade-connected self-excited reactive power compensator 101 includes N single-phase power converters (for example, a single-phase full-bridge voltage type PWM converter) of N units per phase (where N is a natural number of 2 or more, for example). It is configured to be connected in series on the side, and multi-level voltage output is possible. A cascade-connected self-excited reactive power compensator 101 that is directly connected to a three-phase AC system without a transformer is connected to a reactor L _ac on the AC side and includes a total of N × 3 single-phase power converters. . Hereinafter, the “number of units per phase” of a unit including a single-phase power converter and a capacitor connected to the single-phase power converter is referred to as “the number of stages”. As the number of single-phase power converters increases, the number of levels of the phase voltage and the line voltage on the AC side of the self-excited reactive power compensator increases, so that harmonic current can be suppressed.

  Since the self-excited reactive power compensator ideally inputs / outputs only reactive power, not active power, to / from the connected distribution system, the active power stored in the capacitor is not discharged. However, in an actual self-excited reactive power compensator, the active power stored in the capacitor gradually decreases and the DC capacitor voltage decreases due to switching loss and conduction loss in the single-phase power converter. If the capacitor falls short of the charging voltage, the self-excited reactive power compensator cannot stably generate reactive power.

  Therefore, in the actual self-excited reactive power compensator, the capacitor can maintain a predetermined DC voltage value by appropriately taking in the active power corresponding to the loss in the single-phase power converter from the AC system side and charging the capacitor. I am doing so.

  In addition, a motor drive that drives a large-capacity motor is configured by cascading (cascading) a plurality of single-phase power converters (for example, a single-phase full-bridge voltage type PWM converter) having a battery on the DC side. (See, for example, Non-Patent Document 2). This motor drive is directly connected to the motor without a transformer.

J. et al. S. Lai, J.S. Z. FZ Peng, "Multilevel Converters-A New Type of Power Converters", 1996, Transactions of the Institute of Electrical and Electronics Engineers (IEEE) Transactions on (Industry Applications), Vol. 32, no. 3, p. 509-517 L. M.M. LM Tolbert, F.M. Z. Pen (FZ Peng), T.W. G. TG Habettler, “Multilevel Converters for Large Electric Drives”, 1999, Transactions of Industrialization of the Institute of Electrical and Electronics Engineers (IEEE) Vol. 35, no. 1, p. 36-44

  In a cascade-connected self-excited reactive power compensator or power storage device, it is difficult to maintain a uniform DC voltage value for all of a large number of capacitors or power storage elements. Since the switching loss and conduction loss in the single-phase power converter are different in each single-phase power converter, they cannot be controlled collectively. In addition, it is very difficult to stably control the DC voltage value of the capacitor or the power storage element in a transient state when a disturbance occurs in the distribution system. If the DC voltage value of each capacitor or power storage element becomes non-uniform, distortion occurs in the voltage on the AC side of the self-excited reactive power compensator or power storage device, and the self-excited reactive power compensator or power storage device is connected. Harmonic current increases in the connected system. In addition, since the voltage applied to the semiconductor switching element in the single-phase power converter changes, dielectric breakdown is likely to occur in the semiconductor switching element.

  Therefore, in view of the above problems, an object of the present invention is to provide a direct current of each single-phase power converter of a self-excited reactive power compensator or a power storage device configured by cascading the AC sides of a plurality of single-phase power converters. Self-excited reactive power compensator capable of stably and reliably controlling the DC voltage value of a capacitor or a power storage element connected to each side in a steady state as well as a transient state, and this self-excited reactive power compensator A capacitor voltage control method, a power storage device, and a power storage device control method are provided.

  In order to achieve the above object, in the first aspect of the present invention, reactive power is generated in a self-excited reactive power compensator configured by cascading AC sides of a plurality of single-phase power converters. The DC voltage average value is calculated by taking the sum of the DC voltage values of all capacitors provided on the DC side of each single-phase power converter as the DC voltage source used for the DC power source, and this DC voltage average value is equal to the predetermined command value. In addition, the DC voltage value of each capacitor is controlled by switching the semiconductor switching element in each single-phase power converter so that each DC voltage value matches the DC voltage average value.

  That is, the self-excited reactive power compensator according to the first aspect of the present invention calculates the DC voltage average value by taking the sum of DC voltage values of all capacitors provided on the DC side of each single-phase power converter. Means, first DC capacitor voltage control means for generating a first switching command value for matching the DC voltage average value to a predetermined command value, and for matching each DC voltage value to the DC voltage average value Second DC capacitor voltage control means for generating a second switching command value for each single-phase power converter, and each single-phase using the first switching command value and the second switching command value The DC voltage value of each capacitor is controlled by switching control of the semiconductor switching element in the power converter.

  In particular, in the self-excited reactive power compensator provided with a three-phase set of single-phase power converters in which the AC side is cascade-connected and directly connected to a three-phase AC system without a transformer, the first DC capacitor voltage control means includes: The d-axis current value calculated by dq coordinate conversion of the difference between the predetermined command value and the DC voltage average value calculated for each phase by the calculation means and the three-phase current value on the AC side of the self-excited reactive power compensator The first switching command value for each phase is preferably generated using

  Further, in the second aspect of the present invention, as a DC voltage source used to supply power to the AC side of a power storage device configured by cascade-connecting AC sides of a plurality of single-phase power converters. The DC voltage average value is calculated by taking the sum of the DC voltage values of the power storage elements provided on the DC side of each single-phase power converter, and this DC voltage average value matches the predetermined command value, and each DC The DC voltage value of each power storage element is controlled by switching the semiconductor switching element in each single-phase power converter so that the voltage value matches the DC voltage average value.

  That is, the power storage device according to the second aspect of the present invention calculates the DC voltage average value by taking the sum of the DC voltage values of all the power storage elements connected to the DC side of each single-phase power converter. Arithmetic means, first power storage element voltage control means for generating a first switching command value for making the DC voltage average value coincide with a predetermined command value, and making each DC voltage value coincide with the DC voltage average value Second power storage element voltage control means for generating a second switching command value for each single-phase power converter, and using the first switching command value and the second switching command value By switching control of the semiconductor switching element in each single-phase power converter, the DC voltage value of each power storage element is controlled.

  In particular, the power storage device according to the second aspect of the present invention preferably further includes active power control means for generating a third switching command value having the same phase as each phase current on the AC side of the power storage device, By supplying switching control to the semiconductor switching element in each single-phase power converter using the first switching command value, the second switching command value, and the third switching command value, the power is supplied to the AC side of the power storage device. The DC voltage value of each power storage element is controlled while controlling the power.

  According to the present invention, the AC sides of a plurality of single-phase power converters are connected to the DC side of each single-phase power converter of a self-excited reactive power compensator or power storage device configured by cascading each other. The DC voltage value of the capacitor or the power storage element can be stably and reliably controlled not only in the steady state but also in the transient state, and the reactive power output or the active power output can be stably controlled.

FIG. 1 is a principle block diagram showing a DC capacitor voltage control block in a self-excited reactive power compensator according to a first embodiment of the present invention. Hereinafter, components having the same reference numerals in different drawings mean components having the same functions. FIG. 2 is a schematic block diagram of the entire system in the self-excited reactive power compensator according to the first embodiment of the present invention. The DC voltage values V _Du1 , V _Du2 , V _Du3 , V _Dv1 , V _Dv2 , V _Dv3 , V _Dw1 , V _Dw2 and V _Dw3 of each capacitor are detected by the DC voltage detector 30. FIG. 3 is a block diagram showing a control unit including a reactive power control block and a DC capacitor control block in the self-excited reactive power compensator according to the first embodiment of the present invention. The control unit shown in FIG. 3 is configured as a DSP indicated by reference numeral 2 in FIG. FIG. 4 is a circuit diagram showing a circuit configuration of a single-phase power converter in the self-excited reactive power compensator according to the first embodiment of the present invention. FIG. 4 shows a specific circuit configuration of “single-phase full-bridge voltage type PWM converter, capacitor and reactor” which is a block indicated by reference numeral 4 in FIG.

In the first embodiment of the present invention, the self-excited reactive power compensator 1 is constituted by a single-phase full-bridge voltage type PWM converter having three stages per phase. The self-excited reactive power compensator 1 according to the first embodiment of the present invention includes three sets of three-phase single-phase full-bridge voltage type PWM converters in which the AC side is cascade-connected, and is transformerless in a three-phase AC system. Connected directly at. A capacitor serving as a DC voltage source for generating reactive power is connected to the DC side of each single-phase full-bridge voltage type PWM converter. A reactor _Lac is provided on the AC side of the self-excited reactive power compensator 1. For example, an IGBT is used as the semiconductor switching element in the single-phase full-bridge voltage type PWM converter. It should be noted that the number of stages is three, the single-phase power converter is a single-phase full-bridge voltage type PWM converter, and the use of IGBTs as semiconductor switching elements is merely an example and limits the present invention. Instead, other stages, other converters, and other semiconductor switching elements may be used. In the first embodiment of the present invention, the Y connection is used, but a Δ connection may be used.

  The DC capacitor voltage control block 10 according to the present invention is configured as a digital control system in the DSP 2 together with the reactive power control block 20, as shown in FIG. Here, the DC capacitor voltage control block 10 will be described with reference to FIG.

The calculation means 11 shown in FIG. 1 calculates a DC voltage average value from the sum of all capacitors provided on the DC side of each single-phase power converter for each phase. For example As for the u-phase, the calculating means 11, the DC voltage value V _DU1 capacitor of each stage, V _DU2, and V _DU3 sum of _{(V DU1 + V DU2 + V} DU3), the DC voltage average value V _DUave (= ( V _DU1 + V _DU2 + V _DU3 ) / 3) is calculated.

The first DC capacitor voltage control means 12 shown in FIG. 1 has first switching command values S _Au and S for matching the DC voltage average value calculated by the calculation means 11 for each phase with a predetermined command value V _Dref. “Phase-specific DC capacitor voltage control” for generating _Av and S _Aw is performed. At this time, the first switching command values S _Au , S _Av , and S _Aw are obtained by further using the d-axis current value calculated by dq coordinate conversion of the three-phase current value on the AC side of the self-excited reactive power compensator. Preferably it is produced. For example, for the u phase, the first DC capacitor voltage control means 12 determines the difference between the predetermined command value V _Dref and the DC voltage average value V _DUave and the three-phase current on the AC side of the self-excited reactive power compensator 1. by using the d-axis current value i _d, which is calculated by dq coordinate conversion value, they generate a first switching command values S _a. When the phase reference of the phase voltage of the distribution system in which the self-excited reactive power compensator 1 is installed is sin ωt, the first switching command value S _A is created so as to have a phase component of sin ωt. Note that the first switching command value may be generated by detecting each phase current on the AC side of the power storage device and applying an appropriate gain thereto.

The second DC capacitor voltage control means 13-1, 13-2 and 13-3 shown in FIG. 1 set the second switching command value for making each DC voltage value coincide with the DC voltage average value. “Interstage DC capacitor voltage control” is generated for each power converter. In other words, the interstage DC capacitor voltage control is a control in which the voltage value of the capacitor, which is different for each stage, is made to coincide with the same DC voltage value (particularly the DC voltage average value). For example, the u phase is as follows. That is, the second DC capacitor voltage control means 13-1 generates the second switching command value S _Bu1 using the difference between the DC voltage value V _DU1 and the DC voltage average value V _DUave . Further, the second DC capacitor voltage control means 13-2 generates the second switching command value S _Bu2 using the difference between the DC voltage value V _DU2 and the DC voltage average value V _DUave . The second DC capacitor voltage control means 13-3 includes a DC voltage value V _DU3 and a DC voltage average value V _DUave obtained by the calculation means 11 using the DC voltage value V _DU3 for the average calculation process. A second switching command value S _Bu3 is generated using the difference between the two. Note that when the phase reference of the phase voltage of the distribution system in which the self-excited reactive power compensator 1 is installed is sin ωt, the second switching command values S _Bu1 , S _Bu2 and S _Bu3 have a phase component of cos ωt. To be created.

In the DC capacitor voltage control block 10 in the DSP 2 of FIG. 3, the DC voltage value of the capacitor at each stage is obtained by adding the first switching command value and the second switching command value generated as described above. A switching command value for the single-phase full-bridge voltage type PWM converter for controlling the output is generated. For example, for the u phase, switching command values S _u1 , S _u2 and S _u3 are generated for three-stage DC capacitor voltage control.

  On the other hand, regarding the switching command value for the single-phase full-bridge voltage type PWM converter for reactive power control, the three-phase current value input from the A / D converter 8 in the reactive power control block 20 in the DSP 2 of FIG. Further, it may be generated by a known method from the three-phase voltage value and the power supply synchronization information input from the PLL (Phase Locked Loop) (reference numeral 7).

  As shown in FIG. 2, in the DSP 2, the switching command value for direct current capacitor voltage control and the switching command value for reactive power control are superimposed to control the semiconductor switching element in the full bridge voltage type PWM converter. A final switching command value is generated for this purpose. In the first embodiment of the present invention, since the self-excited reactive power compensator 1 is composed of three single-phase full-bridge voltage type PWM converters per phase, there are nine single-phase full-bridge voltage type PWM converters. Therefore, the DSP 2 generates nine types of final switching command values.

  The switching command value generated by the DSP 2 is input to the PWM generator 3. The PWM generator 3 is composed of, for example, an FPGA. Since there are a total of 36 semiconductor switching elements in the nine single-phase full-bridge voltage type PWM converters, the PWM generator 3 has a total of 36 types for switching control of these 36 semiconductor switching elements. PWM signal is generated.

  FIG. 5 is a circuit diagram illustrating a starting method of the self-excited reactive power compensator according to the first embodiment of the present invention. As described above, in the first embodiment of the present invention, the self-excited reactive power compensator 1 is configured by a single-phase full-bridge voltage type PWM converter using an IGBT as a switching element. When all the gates of the single-phase full-bridge voltage type PWM converter are opened, the single-phase full-bridge voltage type PWM converter can be regarded as a single-phase full-bridge diode rectifier from the AC side. In the first embodiment of the present invention, before starting the self-excited reactive power compensator 1, all the gates of each single-phase full-bridge voltage type PWM converter are opened, and the single-phase full-bridge voltage type PWM converter is single-ended. The AC system voltage is rectified by operating as a phase full-bridge diode rectifier, and each capacitor is initially charged using the DC voltage obtained thereby. Since the cascade-connected self-excited reactive power compensator inevitably has a large number of capacitors, it is not preferable in terms of cost and device volume to provide an independent power source for initial charging of each capacitor. In the first embodiment, such an independent power source is not necessary.

The switch MC1 is a switch that connects the self-excited reactive power compensator 1 and the power distribution system, and is provided in each phase. A switch MC2 and a current limiting resistor R connected in parallel to each other are provided between the switch MC1 and the reactor _Lac .

  Here, a specific operation for initial charging the capacitors and starting the self-excited reactive power compensator when each capacitor is not charged at all will be described. First, all the gates of each single-phase full bridge voltage type PWM converter are opened, the switch MC2 is opened, and the switch MC1 is closed. Thereby, each single phase full bridge voltage type PWM converter operates as a single phase full bridge diode rectifier, and an AC voltage is rectified. Each capacitor is gradually charged by the obtained DC voltage. MC2 is closed when each capacitor reaches a predetermined DC voltage value, that is, when charging is completed. Thereby, the power distribution system and the self-excited reactive power compensator 1 are directly connected. When the IGBT switching control in each single-phase full bridge voltage type PWM converter is started, the self-excited reactive power compensator 1 starts the reactive power compensation operation.

  As described above, the DC voltage obtained by operating the single-phase full-bridge voltage type PWM converter as a single-phase full-bridge diode rectifier is used as a starting power source for each control circuit in the self-excited reactive power compensator. Alternatively, a storage means for storing a DC voltage for this purpose may be provided.

  Next, experimental results using a mini-model of the three-phase self-excited reactive power compensator according to the first embodiment of the present invention will be shown. In this experiment, a three-phase self-excited reactive power compensator is configured by cascading single-phase full-bridge voltage type PWM converters per phase in three stages, and the reactive power compensation amount is 10 kVA (var), provided on the AC side. The reactor was 1.2 mH, the capacity of each capacitor was 16400 μF, and the DC capacitor voltage was 60 to 70V. Further, an IGBT having a rating of 600 V and 150 A was used as a semiconductor switching element in the single-phase full-bridge voltage type PWM converter. The carrier frequency of the PWM generator was 1 kHz. Experimental results of installing such a self-excited reactive power compensator in a 50 Hz, three-phase 200 V distribution system are shown in FIGS.

FIG. 6 is a diagram showing an experimental result of the initial charging operation in the self-excited reactive power compensator according to the first embodiment of the present invention. In this figure, the u-phase voltage v _u [V] of the distribution system in which the self-excited reactive power compensator is installed, the current i [A] flowing into the self-excited reactive power compensator, and the DC voltage V _D [ V] is shown. When the initial charging operation described above is started at time 0 second, it can be seen that charging of the capacitor is completed after time 300 milliseconds.

FIG. 7 is a diagram showing an experimental result on the start of operation after completion of initial charging in the self-excited reactive power compensator according to the first embodiment of the present invention. In this figure, the u-phase voltage v _u [V] of the distribution system in which the self-excited reactive power compensator is installed, the current i [A] flowing into the self-excited reactive power compensator, the reactive power q [kVA], The DC voltage V _D [V] of the capacitor is shown. In this experiment, when the reactive power command value q _ref is set to 1 kVA and the operation of the self-excited reactive power compensator is started at the time of 50 milliseconds, a normal reactive power compensation operation is performed after the time of 100 milliseconds. You can see that it is made.

FIG. 8 is a diagram showing experimental results when the self-excited reactive power compensator according to the first embodiment of the present invention is changed from the reactor operation to the capacitor operation. In this figure, the u-phase voltage v _u [V] of the distribution system in which the self-excited reactive power compensator is installed, the current i [A] flowing into the self-excited reactive power compensator, the reactive power q [kVA], The DC voltage V _D [V] of the capacitor is shown. In this experiment, the reactive power command value q _ref was changed from −10 kVA for instructing reactor operation to 10 kVA for instructing capacitor operation. It can be seen that the reactive energy q follows the reactive power command value q _ref satisfactorily with no steady-state deviation during both the reactor operation and the capacitor operation. The reason why the ripple of 100 Hz exists in the DC voltage value of each capacitor is that the active power flowing into the DC side of the single-phase full-bridge voltage type PWM converter has a harmonic component that is twice the commercial frequency. As shown in FIG. 8, the DC voltage command value of each capacitor is linearly controlled from 60 V to 70 V in accordance with the reactive power command value q _ref .

FIG. 9 is a diagram showing experimental results on the characteristics of DC capacitor voltage control in the self-excited reactive power compensator according to the first embodiment of the present invention. In this figure, the DC voltage V _D [V] of each capacitor is shown. In this experiment, in the state where the second DC capacitor voltage control is stopped and only the first DC capacitor voltage control is operated to make the DC voltage value of the capacitor non-uniform, the above-described operation is performed at the time of 100 milliseconds. The second DC capacitor control operation was started. It can be seen that the DC voltage value of each capacitor can be uniformly controlled after the time of 350 milliseconds.

  From the experimental results of FIGS. 6 to 9 described above, it can be seen that the DC capacitor voltage control method of the self-excited reactive power compensator according to the first embodiment of the present invention is effective.

FIG. 10 is a principle block diagram showing a power storage element voltage control block in the power storage device according to the second embodiment of the present invention. FIG. 11 is a schematic block diagram of the entire system in the power storage device according to the second embodiment of the present invention. DC voltage values V _Du1 , V _Du2 , V _Du3 , V _Dv1 , V _Dv2 , V _Dv3 , V _Dw1 , V _Dw2 and V _Dw3 of each power storage device are detected by a DC voltage detector 30. FIG. 12 is a block diagram showing a control unit including an active power / reactive power control block and a DC capacitor / battery control block in the power storage device according to the second embodiment of the present invention. The control unit shown in FIG. 12 is configured as a DSP indicated by reference numeral 2 in FIG.

  The circuit configuration of the single-phase power converter in the power storage device according to the second embodiment of the present invention is obtained by replacing the capacitors of the single-phase power converters in the circuit diagram of FIG. 4 with power storage elements. Other circuit components and modifications thereof are the same as those in the first embodiment of the present invention, and detailed description thereof will be omitted. Examples of the power storage element include a DC capacitor, an electric double layer capacitor, or a battery. According to the second embodiment of the present invention, as in the first embodiment of the present invention, the power storage device is configured by a single-phase full-bridge voltage type PWM converter having three stages per phase.

The calculation means 11 shown in FIG. 10 calculates the DC voltage average value from the sum of all capacitors provided on the DC side of each single-phase power converter for each phase, as in the case of the first embodiment described above. Is. For example As for the u-phase, the calculating means 11, the DC voltage value V _DU1 capacitor of each stage, V _DU2, and V _DU3 sum of _{(V DU1 + V DU2 + V} DU3), the DC voltage average value V _DUave (= ( V _DU1 + V _DU2 + V _DU3 ) / 3) is calculated.

The first DC capacitor / battery voltage control means 12 ′ shown in FIG. 10 has a first switching command value S for matching the DC voltage average value calculated by the calculation means 11 for each phase with a predetermined command value V _Dref. “Phase-specific DC capacitor / battery voltage control” for generating _Au , S _Av , and S _Aw is performed. At this time, the first switching command values S _Au , S _Av , and S _Aw are generated by further using the d-axis current value calculated by dq coordinate conversion of the three-phase current value on the AC side of the power storage device. Is preferred. For example, with respect to the u phase, the first DC capacitor / battery voltage control means 12 ′ determines the difference between the predetermined command value P _ref / V _Dref and the DC voltage average value V _DUave, and the three on the AC side of the power storage device. _A first switching command value S _A is generated using a d-axis current value i _d calculated by dq coordinate conversion of the phase current value. In addition, when the phase reference of the phase voltage of the distribution system in which the power storage device is installed is sin ωt, the first switching command value S _A is created so as to have a phase component of sin ωt. Note that the first switching command value may be generated by detecting each phase current on the AC side of the power storage device and applying an appropriate gain thereto.

The second DC capacitor / battery voltage control means 13-1 ′, 13-2 ′ and 13-3 ′ shown in FIG. 10 first converts each DC voltage value to DC as in the case of the first embodiment. “Inter-stage DC capacitor / battery voltage control” is performed for generating a second switching command value for matching with the voltage average value for each single-phase power converter. In other words, the interstage DC capacitor / battery voltage control is a control that attempts to make the voltage value of the capacitor, which is different for each stage, coincide with the same DC voltage value (particularly the DC voltage average value). Further, the second DC capacitor / battery voltage control means 13-1 ′, 13-2 ′ and 13-3 ′ provide a third switching command value having the same phase as the system current on the AC side of the power storage device. Generate. For example, the u phase is as follows. That is, the second DC capacitor / battery voltage control means 13-1 ′ uses the DC voltage value V _DU1 and the DC voltage average value V _DUave to _generate the second switching command value and the third switching command value S _Bu1. Is generated. Further, the second DC capacitor / battery voltage control means 13-2 ′ uses the DC voltage value V _DU2 and the DC voltage average value V _DUave to _generate the second switching command value and the third switching command value S _Bu2. Is generated. Further, the second DC capacitor / battery voltage control means 13-3 ′ uses the DC voltage value V _DU3 and the DC voltage average value V _DUave to _generate the second switching command value and the third switching command value S _Bu3. Is generated. When the phase reference of the phase voltage of the distribution system (that is, the AC side) in which the power storage device is installed is sin ωt, the second switching command value is created so as to have a phase component of cos ωt, and the third switching The command value is created so as to have a phase component of sin ωt. Note that the third switching command value may be generated by detecting each phase current on the AC side of the power storage device and applying an appropriate gain thereto.

In the DC capacitor / battery voltage / power control block 10 ′ in the DSP 2 of FIG. 12, the first switching command value, the second switching command value, and the third switching command value generated as described above are added. Thus, a switching command value for the single-phase full-bridge voltage type PWM converter for controlling the DC voltage value of the capacitor at each stage is generated while controlling the power to be supplied to the AC side of the power storage device. For example, for the u phase, switching command values S _u1 , S _u2 and S _u3 are generated for three-stage DC capacitor / battery voltage / power control.

  On the other hand, regarding the switching command value for the single-phase full-bridge voltage type PWM converter for active power control and reactive power control, the A / D converter 8 in the active power / reactive power control block 20 ′ in the DSP 2 of FIG. May be generated by a known method from the three-phase current value and the three-phase voltage value input from, and the power supply synchronization information input from the PLL (Phase Locked Loop) (reference numeral 7). For example, if a switching command value that makes the reactive power output zero (0) is created, only active power control is realized.

  As shown in FIG. 11, in the DSP 2, the switching command value for DC capacitor / battery voltage control and the switching command value for active power / reactive power control are superimposed, and the semiconductor in the full bridge voltage type PWM converter A final switching command value for switching control of the switching element is generated. In the second embodiment of the present invention, the power region device is constituted by three single-phase full-bridge voltage type PWM converters per phase, so there are nine single-phase full-bridge voltage type PWM converters, and therefore DSP2 Generates nine types of final switching command values.

  The switching command value generated by the DSP 2 is input to the PWM generator 3. The PWM generator 3 is composed of, for example, an FPGA. Since there are a total of 36 semiconductor switching elements in the nine single-phase full-bridge voltage type PWM converters, the PWM generator 3 has a total of 36 types for switching control of these 36 semiconductor switching elements. PWM signal is generated.

  Next, experimental results using a mini-model of the three-phase power storage device according to the second embodiment of the present invention will be shown. In this experiment, the three-phase power storage device is configured by cascading three-phase single-phase full-bridge voltage type PWM converters per phase, the effective power output amount is 10 kW, the reactor provided on the AC side is 1.2 mH, The capacity of each DC capacitor as an electrical storage element was 0.9 F, and the capacitor voltage was 60 to 70V. Further, an IGBT having a rating of 600 V and 150 A was used as a semiconductor switching element in the single-phase full-bridge voltage type PWM converter. The carrier frequency of the PWM generator was 1 kHz. Experimental results of installing such a power storage device in a 50 Hz, three-phase 200 V distribution system are shown in FIGS.

FIG. 13 is a diagram showing experimental results when the power storage device according to the second example of the present invention is changed from the discharging operation to the charging operation. In this figure, the u-phase voltage v _u [V] of the distribution system in which the power storage device is installed, the current i [A] flowing into the power storage device, the active power p [kW], and the DC voltage V _{D of} each capacitor. [V] is shown. In this experiment, the DC voltage command value V _Dref was changed from 65 V to 80 V in a ramp shape in 20 milliseconds (one cycle). It can be seen that the active power amount p is well controlled even during the transition.

FIG. 14 is a diagram showing experimental results on the characteristics of the DC capacitor / battery voltage control in the power storage device according to the second example of the present invention. The DC voltage V _D [V] of each capacitor is shown. In this experiment, the capacity of the capacitor of the single-phase full-bridge voltage type PWM converter for one phase is 1.1F, the capacity of the capacitor of the single-phase full-bridge voltage type PWM converter for the remaining two phases is 0.9F, In the state where the capacity was unevenly generated and started up, the above-described second DC capacitor / battery voltage control operation was started at the time of 2 milliseconds. It can be seen that the DC voltage value of each capacitor can be controlled uniformly after about 20 milliseconds.

  From the experimental results shown in FIGS. 13 and 14, it can be seen that the power storage device control method according to the second embodiment of the present invention is effective.

  According to the present invention, a self-excited reactive power compensator or a power storage device (cascade-connected self-excited reactive power compensator or power storage device) configured by cascade-connecting AC sides of a plurality of single-phase power converters. Thus, the DC voltage value of the capacitor or power storage element respectively connected to the DC side of each single-phase power converter can be stably controlled not only in the steady state but also in the transient state. Further, it is possible to satisfactorily control the reactive power and the active power in both the steady state and the transient state. The effectiveness of the self-excited reactive power compensator and the power storage device according to the present invention is as shown in the experimental results.

  The self-excited reactive power compensator and the power storage device according to the present invention can be installed in a distribution system without using a commercial frequency transformer, that is, without a transformer, and thus are very advantageous in terms of weight, volume, and cost. is there. In addition, the self-excited reactive power compensator according to the present invention can be easily realized at low cost without the need for initial charging of the capacitor before starting and an independent power source for stabilizing the voltage.

FIG. 3 is a principle block diagram showing a DC capacitor voltage control block in the self-excited reactive power compensator according to the first embodiment of the present invention. 1 is a schematic block diagram of the entire system in a self-excited reactive power compensator according to a first embodiment of the present invention. It is a block diagram which shows the control part which consists of a reactive power control block and a direct-current capacitor control block in the self-excitation reactive power compensator by the 1st Example of this invention. It is a circuit diagram which shows the circuit structure of the single phase power converter in the self-excited reactive power compensator by the 1st Example of this invention. It is a circuit diagram explaining the starting method of the self-excited reactive power compensator according to the first embodiment of the present invention. It is a figure which shows the experimental result about the initial stage charge operation | movement in the self-excited reactive power compensation apparatus by 1st Example of this invention. It is a figure which shows the experimental result about the driving | operation start after completion | finish of initial stage charge in the self-excited reactive power compensation apparatus by 1st Example of this invention. It is a figure which shows the experimental result when changing the self-excited reactive power compensation apparatus by 1st Example of this invention from a reactor operation to a capacitor | condenser operation | movement. It is a figure which shows the experimental result about the characteristic of DC capacitor voltage control in the self-excited reactive power compensator by the 1st Example of this invention. It is a principle block diagram which shows the power storage element voltage control block in the electric power storage apparatus by 2nd Example of this invention. It is a schematic block diagram of the whole system in the electric power storage apparatus in 2nd Example of this invention. It is a block diagram which shows the control part which consists of an active power / reactive power control block and a DC capacitor / battery control block in the electric power storage apparatus by 2nd Example of this invention. It is a figure which shows the experimental result when changing the electric power storage apparatus by the 2nd Example of this invention from discharge operation to charge operation. It is a figure which shows the experimental result about the characteristic of DC capacitor / battery voltage control in the electric power storage apparatus by the 2nd Example of this invention. It is a circuit block diagram which illustrates a general cascade connection type (Y connection) three-phase self-excited reactive power compensator.

Explanation of symbols

1 Self-excited reactive power compensator 2 DSP
3 PWM generator 10 DC capacitor voltage control block 10 'DC capacitor / battery voltage control block 11 arithmetic means 12 first DC capacitor voltage control means 12' first DC capacitor / battery voltage control means 13-1, 13-2 , 13-3 Second DC capacitor voltage control means 13-1 ′, 13-2 ′, 13-3 ′ Second DC capacitor / battery voltage control means 20 Reactive power control block 20 ′ Active power / reactive power control block

Claims (24)

Self-excited reactive power that is configured by cascade-connecting AC sides of a plurality of single-phase power converters and generating reactive power using a capacitor connected to the DC side of each single-phase power converter as a DC voltage source A compensation device,
An arithmetic means for calculating the DC voltage average value by taking the sum of the DC voltage values of all the capacitors;
First DC capacitor voltage control means for generating a first switching command value for making the DC voltage average value coincide with a predetermined command value;
Second DC capacitor voltage control means for generating a second switching command value for matching each DC voltage value with the DC voltage average value for each single-phase power converter;
With
Controlling the DC voltage value of each of the capacitors by performing switching control of the semiconductor switching element in each of the single-phase power converters using the first switching command value and the second switching command value. A self-excited reactive power compensator characterized. The self-excited reactive power compensator according to claim 1, comprising a set of single-phase power converters that are cascade-connected on an AC side and having three phases, and is directly connected to a three-phase AC system without a transformer.
The first DC capacitor voltage control means uses the difference between the predetermined command value and the DC voltage average value calculated for each phase by the calculation means, and the first switching command value for each phase. Produces
The second DC capacitor voltage control means uses the difference between each DC voltage value and the DC voltage average value obtained by using the DC voltage value for the average calculation processing by the calculation means. A self-excited reactive power compensator that generates the second switching command value for each single-phase power converter. The self-excited reactive power compensator according to claim 1, comprising a set of single-phase power converters that are cascade-connected on an AC side and having three phases, and is directly connected to a three-phase AC system without a transformer.
The first DC capacitor voltage control means includes a difference between the predetermined command value and the DC voltage average value calculated for each phase by the calculation means, and a three-phase current on the AC side of the self-excited reactive power compensator. The first switching command value for each phase is generated using a d-axis current value calculated by converting the value by dq coordinate,
The second DC capacitor voltage control means uses the difference between each DC voltage value and the DC voltage average value obtained by using the DC voltage value for the average calculation processing by the calculation means. A self-excited reactive power compensator that generates the second switching command value for each single-phase power converter.   The self-excited reactive power compensator according to claim 1, wherein the single-phase power converter is a single-phase full-bridge voltage type PWM converter.   Before starting the self-excited reactive power compensator, by opening all the gates of the single-phase full bridge voltage type PWM converter and operating the single phase full bridge voltage type PWM converter as a single phase full bridge diode rectifier The self-excited reactive power compensator according to claim 4, wherein the capacitor is initially charged by rectifying an AC system voltage and the obtained DC voltage.   Before starting the self-excited reactive power compensator, by opening all the gates of the single-phase full bridge voltage type PWM converter and operating the single phase full bridge voltage type PWM converter as a single phase full bridge diode rectifier 5. The self-excited reactive power compensator according to claim 4, further comprising power storage means for rectifying an AC system voltage and storing the obtained DC voltage as a starting power source for the self-excited reactive power compensator. In the self-excited reactive power compensator configured by cascading the AC sides of a plurality of single-phase power converters, the DC side of each single-phase power converter as a DC voltage source used to generate reactive power A capacitor voltage control method in a self-excited reactive power compensator that controls the DC voltage value of each capacitor provided,
Each single phase so that the DC voltage average value calculated by taking the sum of the DC voltage values of all the capacitors matches a predetermined command value, and each DC voltage value matches the DC voltage average value. A capacitor voltage control method in a self-excited reactive power compensator characterized by switching control of a semiconductor switching element in a power converter. The self-excited reactive power compensation device according to claim 7, wherein the self-excited reactive power compensator comprising three phases of the single-phase power converters cascaded on the AC side is directly connected to a three-phase AC system without a transformer. A capacitor voltage control method in an apparatus, comprising:
A first DC capacitor voltage control step for generating a first switching command value for each phase using a difference between the predetermined command value and the DC voltage average value calculated for each phase;
Using the difference between each DC voltage value and the DC voltage average value obtained by using the DC voltage value for the average calculation processing by the calculation means, the second voltage for each single-phase power converter is determined. A second DC capacitor voltage control step for generating a switching command value;
With
A self-excited type that controls the DC voltage value of each capacitor by switching control of the semiconductor switching element in each single-phase power converter using the first switching command value and the second switching command value. Capacitor voltage control method in reactive power compensator. The self-excited reactive power compensation device according to claim 7, wherein the self-excited reactive power compensator including three phases of the single-phase power converters cascaded on the AC side is directly connected to a three-phase AC system without a transformer. A capacitor voltage control method in an apparatus, comprising:
D-axis current value calculated by dq coordinate conversion of the difference between the predetermined command value and the DC voltage average value calculated for each phase and the three-phase current value on the AC side of the self-excited reactive power compensator. And a first DC capacitor voltage control step for generating a first switching command value for each phase using:
Using the difference between each DC voltage value and the DC voltage average value obtained by using the DC voltage value for the average calculation processing by the calculation means, the second voltage for each single-phase power converter is determined. A second DC capacitor voltage control step for generating a switching command value;
With
A self-excited type that controls the DC voltage value of each capacitor by switching control of the semiconductor switching element in each single-phase power converter using the first switching command value and the second switching command value. Capacitor voltage control method in reactive power compensator.   The method for controlling a capacitor voltage in a self-excited reactive power compensator according to any one of claims 7 to 9, wherein the single-phase power converter is a single-phase full-bridge voltage type PWM converter.   Before starting the self-excited reactive power compensator, by opening all the gates of the single-phase full bridge voltage type PWM converter and operating the single phase full bridge voltage type PWM converter as a single phase full bridge diode rectifier 11. The capacitor voltage control method in a self-excited reactive power compensator according to claim 10, further comprising an initial charging step of rectifying an AC system voltage and initially charging the capacitor with the obtained DC voltage.   Before starting the self-excited reactive power compensator, by opening all the gates of the single-phase full bridge voltage type PWM converter and operating the single phase full bridge voltage type PWM converter as a single phase full bridge diode rectifier The capacitor voltage control method in the self-excited reactive power compensator according to claim 10, further comprising a power storage step of rectifying an AC system voltage and storing the obtained DC voltage as a starting power source for the self-excited reactive power compensator. . The AC sides of a plurality of single-phase power converters are cascade-connected to each other, and power is supplied to the AC side using a power storage element connected to the DC side of each single-phase power converter as a DC voltage source. A power storage device,
An arithmetic means for calculating a DC voltage average value by taking a sum of DC voltage values of all the power storage elements;
First power storage element voltage control means for generating a first switching command value for making the DC voltage average value coincide with a predetermined command value;
Second power storage element voltage control means for generating a second switching command value for matching each DC voltage value with the DC voltage average value for each single-phase power converter;
With
The DC voltage value of each power storage element is controlled by switching the semiconductor switching element in each single-phase power converter using the first switching command value and the second switching command value. A power storage device characterized by that. Active power control means for generating a third switching command value having the same phase as each phase current on the AC side of the power storage device,
By switching control of the semiconductor switching element in each single-phase power converter using the first switching command value, the second switching command value, and the third switching command value, the power storage device The power storage device according to claim 13, wherein a DC voltage value of each of the power storage elements is controlled while controlling power to be supplied to the AC side. The power storage device according to claim 13, wherein a set of the single-phase power converters in which the AC side is cascade-connected is provided for three phases and is directly connected to a three-phase AC system without a transformer,
The first power storage element voltage control means uses the difference between the predetermined command value and the DC voltage average value calculated by the calculation means for each phase, and uses the first switching command for each phase. Generate a value,
The second power storage element voltage control means uses a difference between each DC voltage value and the DC voltage average value obtained by using the DC voltage value for the average calculation processing by the calculation means, A power storage device that generates the second switching command value for each single-phase power converter. The power storage device according to claim 13, wherein a set of the single-phase power converters in which the AC side is cascade-connected is provided for three phases and is directly connected to a three-phase AC system without a transformer,
The first power storage element voltage control means calculates a difference between the predetermined command value and the DC voltage average value calculated for each phase by the calculation means, and a three-phase current value on the AC side of the power storage device. Using the d-axis current value calculated by dq coordinate conversion, the first switching command value for each phase is generated,
The second power storage element voltage control means uses a difference between each DC voltage value and the DC voltage average value obtained by using the DC voltage value for the average calculation processing by the calculation means, A power storage device that generates the second switching command value for each single-phase power converter.   The power storage device according to any one of claims 13 to 16, wherein the single-phase power converter is a single-phase full-bridge voltage type PWM converter.   The power storage device according to any one of claims 13 to 16, wherein the power storage element is a DC capacitor, an electric double layer capacitor, or a battery. Each of the single-phase power converters has a DC voltage source used to supply power to the AC side of a power storage device configured by cascading the AC sides of a plurality of single-phase power converters. A power storage device control method for controlling a DC voltage value of a power storage element provided,
The DC voltage average value calculated by taking the sum of the DC voltage values of all the power storage elements matches a predetermined command value, and each DC voltage value matches the DC voltage average value. A method of controlling a power storage device, comprising switching control of a semiconductor switching element in a single-phase power converter. 20. The power storage device control method according to claim 19, wherein the power storage device including the three-phase set of single-phase power converters whose AC side is cascade-connected is directly connected to a three-phase AC system without a transformer. ,
A first power storage element voltage control step for generating a first switching command value for each phase using a difference between the predetermined command value and the DC voltage average value calculated for each phase;
Using the difference between each DC voltage value and the DC voltage average value obtained by using the DC voltage value for the average calculation processing by the calculation means, the second voltage for each single-phase power converter is determined. A second power storage element voltage control step for generating a switching command value;
With
The DC voltage value of each power storage element is controlled by switching the semiconductor switching element in each single-phase power converter using the first switching command value and the second switching command value. Power storage device control method. The power storage device control method according to claim 19, wherein the power storage device including three phases of the single-phase power converter groups cascaded on the AC side is directly connected to a three-phase AC system without a transformer. ,
The difference between the predetermined command value and the DC voltage average value calculated for each phase, and the d-axis current value calculated by dq coordinate conversion of the three-phase current value on the AC side of the power storage device, A first power storage element voltage control step for generating a first switching command value for each phase,
Using the difference between each DC voltage value and the DC voltage average value obtained by using the DC voltage value for the average calculation processing by the calculation means, the second voltage for each single-phase power converter is determined. A second power storage element voltage control step for generating a switching command value;
With
The DC voltage value of each power storage element is controlled by switching the semiconductor switching element in each single-phase power converter using the first switching command value and the second switching command value. Power storage device control method. An active power control step of generating a third switching command value having the same phase as each phase current on the AC side of the power storage device;
By switching control of the semiconductor switching element in each single-phase power converter using the first switching command value, the second switching command value, and the third switching command value, the power storage device The power storage device control method according to claim 20 or 21, wherein the DC voltage value of each of the power storage elements is controlled while controlling the power to be supplied to the AC side.   The power storage device control method according to any one of claims 19 to 22, wherein the single-phase power converter is a single-phase full-bridge voltage type PWM converter.   The power storage device control method according to any one of claims 19 to 22, wherein the power storage element is a DC capacitor, an electric double layer capacitor, or a battery.

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