Power converter, control method, and control program

Abstract

To obtain a power converter capable of effectively suppressing voltage variation of a position on a power supply side of a power system than a linkage system point in the power system.SOLUTION: A power converter 1 has: a power conversion part 10 connected between a power system 4 and a load 3 and performing power conversion between the power system 4 and the load 3; and a control part 20 controlling the power conversion part 10. The control part 20 determines a reactive power command value, based on output active power of the power conversion part 10, suppressing voltage variation of a power supply side position that is a position closer to a power supply of the power system 4 than a linkage system point Pa with the power system 4, and controls the power conversion part 10 based on the determined reactive power command value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a power conversion device, a control method, and a control program connected between a power system and a load.

Background Art

[0002] Conventionally, as a method for suppressing voltage fluctuations at a connection point caused by fluctuations in a load connected to a power system, a reactive power compensation method by attaching and detaching a power capacitor is known. However, in the reactive power compensation method using a power capacitor, reactive power compensation becomes discontinuous, and voltage fluctuations occur when the power capacitor is attached and detached, so it is difficult to suppress high-speed voltage fluctuations.

[0003] Therefore, as a method for performing high-speed voltage adjustment, a compensation method using a power conversion device is known. And, as a compensation method using a power conversion device, an AC voltage control method for outputting reactive power so that the voltage at the connection point follows a command value, a fixed power factor method for outputting reactive power at a constant power factor with respect to the output active power of the power conversion device, etc. are known. For example, Patent Document 1 discloses a power conversion device of the fixed power factor method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, while power converters equipped with AC voltage control methods are highly effective in suppressing fluctuations in the interconnection point voltage, they may be less effective in suppressing voltage fluctuations at the power source side of the power system, which is closer to the power source than the interconnection point. In particular, if the electrical characteristics of the power system change, voltage fluctuations at the power source side may not be sufficiently suppressed. Furthermore, when using power converters equipped with a fixed power factor method, the effect of suppressing voltage fluctuations at the power source side may be reduced because reactive power is proportional to the load power.

[0006] This disclosure has been made in view of the above, and aims to provide a power converter that can more effectively suppress voltage fluctuations at a location on the power source side of the power system from the interconnection point in the power system. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the power conversion device of this disclosure comprises a power conversion unit connected between the power system and the load and performing power conversion between the power system and the load, and a control unit that controls the power conversion unit. The control unit is Using a simulation or calculation that simulates the electrical characteristics of the power system, the correlation between the output active power of the power conversion unit and the reactive power command value that suppresses voltage fluctuations at the power source side, which is closer to the power source of the power system than the interconnection point with the power system, is derived in advance. The output active power of the power conversion unit The corresponding reactive power command value The system determines the reactive power command value and controls the power conversion unit based on that value. [Effects of the Invention]

[0008] According to this disclosure, the effect is that voltage fluctuations at locations on the power source side of the power system can be suppressed more effectively than at the interconnection points in the power system. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the configuration of a power system including a power converter according to Embodiment 1. [Figure 2] This figure shows an example of the configuration of a power conversion device according to Embodiment 1. [Figure 3] This figure shows an example of the configuration of the first power converter according to Embodiment 1. [Figure 4]This figure shows an example of the configuration of the first control unit of the power converter according to Embodiment 1. [Figure 5] This figure shows an example of a pattern table for the reactive power command value output unit according to Embodiment 1. [Figure 6] This figure shows an example of the hardware configuration of the control unit of the power converter according to Embodiment 1. [Figure 7] This figure shows an example of the configuration of a power converter according to Embodiment 2. [Figure 8] This figure shows an example of the configuration of the first control unit of the power converter according to Embodiment 2. [Modes for carrying out the invention]

[0010] The power conversion device, control method, and control program according to the embodiment will be described in detail below with reference to the drawings.

[0011] Embodiment 1. Figure 1 is a diagram showing an example of the configuration of a power system including a power converter according to Embodiment 1. As shown in Figure 1, the power system 100 according to Embodiment 1 includes a power converter 1, a transformer 2, a load 3, and a power grid 4.

[0012] The power converter 1 is connected between the power system 4 and the load 3, and performs power conversion between the power system 4 and the load 3. The load 3 is an AC load, such as a three-phase AC conductor or a three-phase AC generator.

[0013] The power converter 1, transformer 2, and load 3 are equipment belonging to electricity consumer 5, and the power converter 1 is connected to the power system 4 via transformer 2. The connection point between the power system 4 and transformer 2 is the interconnection point Pa between the equipment of electricity consumer 5 and the power system 4, and the voltage value Vc at this interconnection point Pa is, for example, a three-phase AC voltage of 66kV or 33kV. The transformer 2 converts the voltage at interconnection point Pa to a 6.6kV three-phase AC voltage, for example, and outputs the converted 6.6kV three-phase AC voltage to the power converter 1.

[0014] Power system 4 is, for example, the commercial power system of a power company. Power system 4 includes a power source 40, a transmission line 41, a transformer 42, and transmission lines 43, 44, and 45. Power source 40 is, for example, a power supply device that outputs a 154kV three-phase AC voltage. Transformer 42 converts the 154kV three-phase AC voltage to a 66kV or 33kV three-phase AC voltage, and outputs the converted 66kV or 33kV three-phase AC voltage to transmission lines 43, 44, and 45.

[0015] The power converter 1 is connected to the power source 40 of the power system 4 via transmission line 41, transformer 42, transmission line 44, and transformer 2. Although not shown in Figure 1, the equipment of other power consumers is also connected to the power source 40 of the power system 4, for example, via transmission line 41, transformer 42, and transmission line 43, or transmission line 41, transformer 42, and transmission line 45.

[0016] In the example shown in Figure 1, the power converter 1 is connected to the power system 4 via the transformer 2, but it may also be connected to the power system 4 without going through the transformer 2. In this case, the connection point between the power converter 1 and the power system 4 is the interconnection point Pa.

[0017] The power converter 1 determines a reactive power command value corresponding to the output active power P, which suppresses fluctuations in the voltage Vcc at the power source side position Pb, and outputs the reactive power corresponding to the determined reactive power command value to the power system 4. The power source side position Pb is a position on the power source 40 side that is farther away from the interconnection point Pa in the power system 4. In the example shown in Figure 1, it is a position on the power source 40 side of the transmission line 44, but it is not limited to this example.

[0018] The output active power P is the active power on the load 3 side. Since the power converter 1 determines the reactive power command value based on the active power on the load 3 side, rather than the active power on the power system 4 side, the control system can be made more stable. The active power on the load 3 side is the active power output from the power converter 1 to the load 3 or the active power output from the load 3 to the power converter 1. Note that the output active power P is not limited to the active power on the load 3 side, but may also be the active power on the power system 4 side.

[0019] Figure 2 shows an example of the configuration of a power conversion device according to Embodiment 1. As shown in Figure 2, the power conversion device 1 comprises a power conversion unit 10 and a control unit 20. The power conversion unit 10 comprises a first power converter 11, a second power converter 12, and a voltage detection unit 13.

[0020] The first power converter 11 is a voltage-type power converter that performs a forward conversion operation to convert AC power to DC power during the powering operation of the load 3, and a reverse conversion operation to convert DC power to AC power during the regenerative operation of the load 3. The first power converter 11 is, for example, a PWM (Pulse Width Modulation) converter and a two-level converter, but it may be a three-level converter or other type of converter.

[0021] Figure 3 shows an example of the configuration of the first power converter according to Embodiment 1. As shown in Figure 3, the first power converter 11 comprises switching elements Q1 to Q6, reverse current prevention diodes D1 to D6, and a gate signal amplification unit 14.

[0022] The first power converter 11 performs power conversion by controlling the on / off state of switching elements Q1 to Q6 by the control unit 20. Switching elements Q1 to Q6 are, for example, IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

[0023] Although not shown in Figure 3, the first power converter 11 includes, for example, a current detection unit for detecting three-phase AC currents Ir, Is, and It, and a voltage detection unit for detecting three-phase AC voltages Vr, Vs, and Vt. The AC current Ir is the instantaneous value of the AC current of the R phase, the AC current Is is the instantaneous value of the AC current of the S phase, and the AC current It is the instantaneous value of the AC current of the T phase. The AC voltage Vr is the instantaneous value of the AC voltage of the R phase, the AC voltage Vs is the instantaneous value of the AC voltage of the S phase, and the AC voltage Vt is the instantaneous value of the AC voltage of the T phase. The first power converter 11 may also include filters such as an LC filter or an LCL filter.

[0024] Returning to Figure 2, let's continue the explanation of the power conversion unit 10. The second power converter 12 of the power conversion unit 10 is a voltage-type power converter. During the traction operation of the load 3, it performs an inverse conversion operation to convert DC power to AC power, and during the regenerative operation of the load 3, it performs a forward conversion operation to convert AC power to DC power.

[0025] The second power converter 12 has multiple switching elements, and performs power conversion by switching these multiple switching elements on and off. The switching elements are, for example, IGBTs or MOSFETs. The second power converter 12 is, for example, a PWM inverter, a two-level inverter, but it may be a three-level inverter or other inverter. The second power converter 12 may include filters such as LC filters or LCL filters.

[0026] The voltage detection unit 13 detects the bus voltage Vpn, which is the instantaneous value of the bus voltage between the DC buses Lp and Ln between the first power converter 11 and the second power converter 12, and outputs a detection signal indicating the detected bus voltage Vpn to the control unit 20.

[0027] The control unit 20 comprises a first control unit 21 and a second control unit 22. The first control unit 21 determines when the bus voltage Vpn detected by the voltage detection unit 13 is a reference value Vpn * The first power converter 11 is controlled to match this.

[0028] The second control unit 22 causes the second power converter 12 to perform an inverse conversion operation when the load 3 is in powering operation, and causes the second power converter 12 to perform a forward conversion operation when the load 3 is in regenerative operation. When the second power converter 12 performs an inverse conversion operation, the bus voltage Vpn decreases, so the first control unit 21 controls the first power converter 11 to perform a forward conversion operation. Also, when the second power converter 12 performs a forward conversion operation, the bus voltage Vpn increases, so the first control unit 21 controls the first power converter 11 to perform an inverse conversion operation.

[0029] The first control unit 21 further determines a reactive power command value to suppress voltage fluctuations at the power supply side position Pb based on the output active power P of the power conversion unit 10, and controls the first power converter 11 based on the determined reactive power command value. As a result, the power conversion device 1 can more effectively suppress voltage fluctuations at the power supply side position Pb shown in Figure 1. The configuration of the first control unit 21 will be described in detail below.

[0030] Figure 4 shows an example of the configuration of the first control unit of the power conversion device according to Embodiment 1. As shown in Figure 4, the first control unit 21 includes a reactive power command value output unit 30, an active power command value output unit 31, a 3-phase 2-phase conversion unit 32, a voltage command value calculation unit 33, and a gate signal generation unit 34.

[0031] The reactive power command value output unit 30 outputs a reactive power command value Q based on the output active power P of the power conversion unit 10 to suppress voltage fluctuations at the power supply side position Pb. * Determine the reactive power command value Q * Outputs a reactive power command value Q that suppresses voltage fluctuations at power supply side position Pb. * This is, for example, the command value for output reactive power such that the voltage at power supply side position Pb is the same as the voltage under no load conditions when the output active power P of the power converter 1 is constant.

[0032] For example, the reactive power command value output unit 30 outputs a reactive power command value Q for each output active power P with a different value. *has an associated pattern table, and based on such a pattern table, a reactive power command value Q based on the output active power P of the power conversion unit 10 * is determined.

[0033] FIG. 5 is a diagram showing an example of a pattern table included in the reactive power command value output unit according to Embodiment 1. The pattern table shown in FIG. 5 is a table in which the output active power P and the reactive power command value Q * are associated for each output active power P with different values.

[0034] In the example shown in FIG. 5, the output active power P of value P1 is associated with the reactive power command value Q of value Q1 * the output active power P of value P2 is associated with the reactive power command value Q of value Q2 * the output active power P of value P3 is associated with the reactive power command value Q of value Q3 * are associated.

[0035] When the pattern table is in the state shown in FIG. 5, the reactive power command value output unit 30, when the output active power P of the power conversion unit 10 is the output active power P of value P1, outputs the reactive power command value Q of value Q1 * when the output active power P of the power conversion unit 10 is the output active power P of value P2, outputs the reactive power command value Q of value Q2 * When the output active power P of the power conversion unit 10 is the output active power P of value P3, the reactive power command value output unit 30 outputs the reactive power command value Q of value Q3 * is output.

[0036] In the pattern table, a plurality of output active powers P with values at regular intervals are included within the load fluctuation range. For example, the difference between value P1 and value P2 is equal to the difference between value P2 and value P3. Note that the plurality of output active powers P set in the pattern table do not have to have a constant interval between values. For example, the interval of the output active power P with a high frequency value may be smaller than the interval of the output active power P with a low frequency value.

[0037] The reactive power command value Q for suppressing voltage fluctuations at the power supply side position Pb *This is calculated, for example, by representing the power system 4 with an equivalent circuit and performing a simulation for each output active power P with a different value. Based on the results calculated in this way, the pattern table described above is set in the reactive power command value output unit 30.

[0038] The electrical characteristics of power system 4 may vary depending on the season, day of the week, and time of day. For example, in power system 4, the electrical characteristics of transmission lines 43, 44, and 45 may vary depending on the season, day of the week, and time of day. In this case, by performing a simulation using the equivalent circuit of power system 4 in the state with the most fluctuating electrical characteristics among the different states of electrical characteristics, a reactive power command value Q that suppresses the voltage fluctuation at power source position Pb will be determined for each different output active power P. * This is calculated.

[0039] Furthermore, a pattern table may be provided in the reactive power command value output unit 30 for each state in which the electrical characteristics of the power system 4 differ. For example, the reactive power command value output unit 30 has a pattern table for each combination of season, day of the week, and time of day, and uses the pattern table corresponding to the current season, day of the week, and time of day from among these pattern tables to determine the reactive power command value Q corresponding to the output active power P of the power conversion unit 10. * It is possible to make a decision.

[0040] Furthermore, the reactive power command value Q suppresses voltage fluctuations at power supply side position Pb. * For example, this could be a reactive power command value calculated for each different output active power P, which minimizes the average value of the voltage fluctuation at the power source side position Pb under multiple conditions with different electrical characteristics of the power system 4.

[0041] Furthermore, the reactive power command value output unit 30 uses a calculation formula instead of the pattern table described above to output a reactive power command value Q corresponding to the active power P. * It is also possible to determine this. The calculation formula is derived from the output active power P to the reactive power command value Q, which can be determined through simulations, etc. *This is a calculation formula for calculating the reactive power command value Q. The reactive power command value output unit 30 uses the calculation formula to calculate the reactive power command value Q from the output active power P of the power conversion unit 10, which is the state with the electrical characteristics in which the voltage at the power source side position Pb of the power system 4 is most likely to fluctuate among states with different electrical characteristics. * Calculate.

[0042] The reactive power command value output unit 30 outputs a reactive power command value Q based on the output active power P of the power conversion unit 10. * The power system 4 may have a configuration in which it has a calculation formula for each state in which its electrical characteristics differ. In this case, the reactive power command value output unit 30 uses a calculation formula corresponding to the current season, day of the week, and time of day to calculate the reactive power command value Q from the output active power P of the power conversion unit 10. * Calculate.

[0043] The output active power P of the power conversion unit 10 is detected, for example, by the second control unit 22 and notified from the second control unit 22 to the first control unit 21. The second control unit 22 calculates the output active power P based on the three-phase AC currents Iu, Iv, Iw and three-phase AC voltages Vu, Vv, Vw detected, for example, by the current detection unit and voltage detection unit (not shown) provided in the second power converter 12, and notifies the first control unit 21 of the calculated output active power P. The AC current Iu is the instantaneous value of the U-phase AC current, the AC current Iv is the instantaneous value of the V-phase AC current, and the AC current Iw is the instantaneous value of the W-phase AC current. Similarly, the AC voltage Vu is the instantaneous value of the U-phase AC voltage, the AC voltage Vv is the instantaneous value of the V-phase AC voltage, and the AC voltage Vw is the instantaneous value of the W-phase AC voltage.

[0044] The reactive power command value output unit 30 outputs a reactive power command value Q based on the output active power P notified by the second control unit 22, which suppresses voltage fluctuations at the power supply side position Pb. * The reactive power command value output unit 30 determines the reactive power command value Q that suppresses voltage fluctuations at power supply side position Pb, by using the active power command value generated by the second control unit 22 as the output active power P instead of the output active power P calculated by the second control unit 22. *It is also possible to make that decision.

[0045] Furthermore, the reactive power command value output unit 30, for example, instead of the output active power P calculated by the second control unit 22, uses the active power command value calculated by the active power command value output unit 31 (described later) as the output active power P to suppress the voltage fluctuation at the power supply side position Pb using a reactive power command value Q. * It is also possible to make that decision.

[0046] The active power command value output unit 31 outputs an active power command value P such that the bus voltage Vpn matches the reference value Vref. * Generates the active power command value P * The output is as follows: For example, the active power command value output unit 31 performs PI (Proportional Integral) control or PID (Proportional Integral Differential) control so that the difference between the bus voltage Vpn and the reference value Vref becomes zero or small, thereby outputting the active power command value P * Generates.

[0047] The 3-phase 2-phase conversion unit 32 converts the 3-phase AC currents Ir, Is, It detected by a current detection unit (not shown) provided in the first power converter 11 into d-axis current Id and q-axis current Iq by 3-phase 2-phase conversion, and outputs the converted d-axis current Id and q-axis current Iq to the voltage command value calculation unit 33. The 3-phase 2-phase conversion unit 32 performs 3-phase 2-phase conversion using, for example, the voltage phases obtained from the 3-phase AC voltages Vr, Vs, Vt.

[0048] The voltage command value calculation unit 33 calculates the reactive power command value Q * Active power command value P * Based on the d-axis current Id and q-axis current Iq output from the 3-phase 2-phase conversion unit 32, the 3-phase voltage command value Vr * ,Vs * ,Vt * The voltage command value calculation unit 33 calculates the calculated 3-phase voltage command value Vr. * ,Vs * ,Vt * This is output to the gate signal generation unit 34.

[0049] The voltage command value calculation unit 33 calculates, for example, the reactive power command value Q * Dividing this by the reference value Vref gives the d-axis current command value Id * Generates the d-axis current command value Id * Perform PI control or PID control so that the difference between the d-axis voltage value Vd and the d-axis current Id is zero or small. * Generates.

[0050] Furthermore, the voltage command value calculation unit 33 calculates, for example, the active power command value P * Dividing this by the reference value Vref gives the q-axis current command value Iq * Generates the q-axis current command value Iq * Perform PI control or PID control so that the difference between the q-axis voltage value Vq and the q-axis current Iq is zero or small. * Generates.

[0051] Then, the voltage command value calculation unit 33 calculates the d-axis voltage value Vd * and the q-axis voltage value Vq * By converting between two phases and three phases, the three-phase voltage command value Vr * ,Vs * ,Vt * The voltage command value calculation unit 33 generates the three-phase voltage command value Vr. * ,Vs * ,Vt * This is output to the gate signal generation unit 34.

[0052] The gate signal generation unit 34 generates a 3-phase voltage command value Vr * ,Vs * ,Vt * Based on this, a gate signal Ga is generated to control multiple switching elements of the first power converter 11. For example, the gate signal generation unit 34 generates a gate signal Ga that controls the three-phase voltage command value Vr * ,Vs * ,Vt * Based on the comparison with the carrier wave, gate signals Ga are generated to drive the switching elements Q1 to Q6 shown in Figure 3. These gate signals Ga are PWM (Pulse Width Modulation) signals.

[0053] The gate signal generation unit 34 outputs the generated gate signal Ga to the gate signal amplification unit 14 of the first power converter 11. The gate signal Ga is amplified by the gate signal amplification unit 14 and output to the switching elements Q1 to Q6. As a result, the power converter 1 can more effectively suppress voltage fluctuations at the power source side position Pb, which is farther away from the interconnection point Pa in the power system 4.

[0054] Figure 6 shows an example of the hardware configuration of the control unit of the power converter according to Embodiment 1. As shown in Figure 6, the control unit 20 of the power converter 1 includes a processor 101 and a computer equipped with memory 102 and bus 103.

[0055] The processor 101 and memory 102 can send and receive information from each other via the bus 103. The processor 101 performs the functions of the first control unit 21 and the second control unit 22 by reading and executing a program stored in memory 102. The processor 101 is, for example, an example of a processing circuit and includes one or more of the following: CPU (Central Processing Unit), DSP (Digital Signal Processor), and system LSI (Large Scale Integration).

[0056] Memory 102 includes one or more of the following: RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). Memory 102 also includes a recording medium on which a computer-readable program is stored. Such a recording medium includes one or more of the following: non-volatile or volatile semiconductor memory, magnetic disk, flexible memory, optical disk, compact disk, and DVD (Digital Versatile Disc). The control unit 20 of the power converter 1 may include integrated circuits such as ASIC (Application Specific Integrated Circuit) and FPGA (Field Programmable Gate Array).

[0057] As described above, the power converter 1 comprises a power conversion unit 10 connected between the power system 4 and the load 3 and performing power conversion between the power system 4 and the load 3, and a control unit 20 that controls the power conversion unit 10. The control unit 20 controls a reactive power command value Q that suppresses voltage fluctuations at the power source side position Pb, which is closer to the power source 40 of the power system 4 than the connection point Pa with the power system 4. * The reactive power command value Q is determined based on the output active power P of the power conversion unit 10. * Based on this, the power conversion unit 10 is controlled. As a result, the power conversion device 1 can more effectively suppress voltage fluctuations at the power source side position Pb, which is a power source side position further away than the interconnection point Pa in the power system 4.

[0058] Furthermore, the control unit 20 uses the active power on the load 3 side as the output active power P, and the reactive power command value Q * This determines the control system of the power converter 1, thereby making it more stable.

[0059] Furthermore, the control unit 20 sets a reactive power command value Q for each output active power P with a different value to suppress voltage fluctuations at the power supply side position Pb. * The system has a pattern table to which the reactive power command value Q controls the power conversion unit 10 using the pattern table. * This determines the reactive power command value Q at power source position Pb. * This can be determined very quickly.

[0060] Furthermore, the control unit 20 calculates the reactive power command value Q from the output active power P of the power conversion unit 10. * The reactive power command value Q controls the power conversion unit 10 based on the calculation result of the calculation formula used to calculate it. * This determines the voltage fluctuation at power supply position Pb, enabling the power converter 1 to more effectively suppress voltage fluctuations at power supply position Pb without using a pattern table.

[0061] Furthermore, the power conversion unit 10 includes a first power converter 11 and a second power converter 12. The first power converter 11 converts AC power supplied from the power system 4 to DC power and converts DC power back to AC power and supplies it to the power system 4. The second power converter 12 converts DC power supplied from the first power converter 11 to AC power and converts AC power supplied from the load 3 back to DC power and supplies it to the first power converter 11. The control unit 20 determines the reactive power command value Q * Based on this, the first power converter 11 is controlled. This makes it possible to more effectively suppress voltage fluctuations at the power source side position Pb in the power converter 1, which performs power conversion between the AC load 3 and the power system 4.

[0062] Embodiment 2. The power converter according to Embodiment 2 differs from the power converter 1 according to Embodiment 1 in that it suppresses voltage fluctuations at the interconnection point Pa in addition to voltage fluctuations at the power source side position Pb. In the following, components having the same functions as in Embodiment 1 are denoted by the same reference numerals and their descriptions are omitted, and the differences from the power converter 1 of Embodiment 1 will be described in detail.

[0063] Figure 7 shows an example of the configuration of a power converter according to Embodiment 2. As shown in Figure 7, the power converter 1A according to Embodiment 2 differs from the power converter 1 according to Embodiment 1 in that it includes a control unit 20A instead of a control unit 20.

[0064] The control unit 20A differs from the control unit 20 in that, instead of the first control unit 21, it includes a first control unit 21A that controls the first power converter 11 in such a way that it suppresses not only voltage fluctuations at the power supply side position Pb but also voltage fluctuations at the interconnection point Pa.

[0065] The first control unit 21A controls the first power converter 11 to suppress voltage fluctuations at the power supply side position Pb, as well as to reduce the deviation of the feedback value Vcf, which is proportional to the voltage value Vc at the interconnection point Pa detected by the voltage sensor 6. As a result, the power converter 1A can suppress voltage fluctuations at the interconnection point Pa in addition to voltage fluctuations at the power supply side position Pb.

[0066] Figure 8 shows an example of the configuration of the first control unit of the power converter according to Embodiment 2. As shown in Figure 8, the first control unit 21A of the power converter 1A according to Embodiment 2 differs from the first control unit 21 of the power converter 1 in that it includes a reactive power command value output unit 30A instead of a reactive power command value output unit 30.

[0067] The reactive power command value output unit 30A comprises a power supply side position voltage control unit 50, a interconnection point voltage control unit 51, multiplication units 52, 53, and an addition unit 54. The power supply side position voltage control unit 50 has the same function as the reactive power command value output unit 30, and determines a reactive power command value Qptn to suppress voltage fluctuations at the power supply side position Pb based on the output active power P of the power conversion unit 10, and outputs the determined reactive power command value Qptn. The reactive power command value Qptn is the reactive power command value Q output by the reactive power command value output unit 30 according to Embodiment 1. * It is the same as this.

[0068] The interconnection point voltage control unit 51 controls the feedback value Vcf output from the voltage sensor 6 and the voltage command value Vc of the interconnection point Pa. *P control or PI control is performed so that the difference with is zero or small, thereby reducing the reactive power command value Q AVR The interconnection point voltage control unit 51 generates the reactive power command value Q. AVR The result is output to the multiplication unit 53.

[0069] The multiplication unit 52 has a gain Kptn and multiplies the reactive power command value Qptn by Kptn and outputs it to the addition unit 54. The multiplication unit 53 has a gain K AVR It has a reactive power command value Q AVR to K AVR The result is multiplied and output to the adder 54.

[0070] The addition unit 54 adds the reactive power command value Qptn multiplied by Kptn and K AVR Doubled reactive power command value Q AVR The two values ​​are added together, and the result of the addition is the reactive power command value Q. * This is output to the voltage command value calculation unit 33. As a result, the voltage command value calculation unit 33 calculates a three-phase voltage command value Vr that suppresses the voltage fluctuations at the power supply side position Pb and the voltage fluctuations at the interconnection point Pa. * ,Vs * ,Vt * It can generate [this].

[0071] In the reactive power command value output unit 30A, gain Kptn and gain K AVR By setting the values ​​to the same value, the effect of suppressing voltage fluctuations at the power supply side position Pb and the effect of suppressing voltage fluctuations at the interconnection point Pa can be obtained equally. Also, the gain Kptn is set to gain K AVR By setting the value to a larger value than this, the effect of suppressing voltage fluctuations at the power supply side position Pb can be made greater than the effect of suppressing voltage fluctuations at the interconnection point Pa. Also, the gain Kptn can be changed to gain K AVR By setting a value smaller than this, the effect of suppressing voltage fluctuations at the power supply side location Pb can be made smaller than the effect of suppressing voltage fluctuations at the interconnection point Pa.

[0072] The hardware configuration example of the control unit 20A of the power converter 1A according to Embodiment 2 is the same as the hardware configuration of the control unit 20 of the power converter 1 shown in Figure 6. The processor 101 can perform the functions of the first control unit 21A and the second control unit 22 by reading and executing the program stored in the memory 102.

[0073] As described above, the control unit 20A of the power converter 1A according to Embodiment 2 sets a reactive power command value Qptn to suppress voltage fluctuations at the power supply side position Pb and a reactive power command value Q to suppress voltage fluctuations at the interconnection point Pa. AVR The reactive power command value Q controls the power conversion unit 10 based on this. * This determines the voltage fluctuations at the interconnection point Pa, in addition to suppressing voltage fluctuations at the power source side location Pb.

[0074] In the example described above, load 3 was assumed to be an AC load, but load 3 may also be a DC load. In this case, the power conversion unit 10 may not have a second power converter 12, and the control units 20, 20A may, for example, control the output active power P or active power command value P of the first power converter 11. * Based on these factors, the reactive power command value Q * To decide.

[0075] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0076] The various aspects of this disclosure are summarized below as an appendix.

[0077] (Note 1) A power conversion unit connected between the power system and the load, which performs power conversion between the power system and the load, The system comprises a control unit for controlling the power conversion unit, The control unit, A reactive power command value is determined based on the output active power of the power conversion unit to suppress voltage fluctuations at the power source side position, which is closer to the power source of the power system than the connection point with the power system, and the power conversion unit is controlled based on the determined reactive power command value. A power conversion device characterized by the following features. (Note 2) The control unit, The reactive power command value is determined by using the active power on the load side as the output active power. The power conversion device described in Appendix 1, characterized by the features described herein. (Note 3) The control unit, The system has a table associated with a reactive power command value that suppresses voltage fluctuations at the power supply side for each output active power with a different value, and the reactive power command value that controls the power conversion unit is determined using the table. A power conversion device as described in Appendix 1 or 2, characterized by the features described herein. (Note 4) The control unit, The reactive power command value for controlling the power converter is determined based on the calculation result of a formula that calculates a reactive power command value from the output active power of the power converter. A power conversion device as described in Appendix 1 or 2, characterized by the features described herein. (Note 5) The control unit, The reactive power command value for controlling the power conversion unit is determined based on the reactive power command value that suppresses voltage fluctuations at the power supply side location and the reactive power command value that suppresses voltage fluctuations at the interconnection point. A power conversion device as described in Appendix 3 or 4, characterized by the features described herein. (Note 6) The power conversion unit is A first power converter that converts AC power supplied from the aforementioned power system to DC power and converts DC power back to AC power and supplies it to the aforementioned power system, The system comprises a second power converter that converts DC power supplied from the first power converter into AC power and converts AC power supplied from the load into DC power and supplies it to the first power converter, The control unit, Based on the determined reactive power command value, the first power converter is controlled. A power conversion device according to any one of the appendices 1 to 5, characterized in that it is a power conversion device. [Explanation of Symbols]

[0078] 1, 1A Power converter, 2, 42 Transformer, 3 Load, 4 Power system, 5 Power consumer, 6 Voltage sensor, 10 Power conversion unit, 11 First power converter, 12 Second power converter, 13 Voltage detection unit, 14 Gate signal amplification unit, 20, 20A Control unit, 21, 21A First control unit, 22 Second control unit, 30, 30A Reactive power command value output unit, 31 Active power command value output unit, 32 3-phase 2-phase conversion unit, 33 Voltage command value calculation unit, 34 Gate signal generation unit, 40 Power supply, 41, 43, 44, 45 Transmission line, 50 Power supply side position voltage control unit, 51 Interconnection point voltage control unit, 52, 53 Multiplication unit, 54 Addition unit, 100 Power system, 101 Processor, 102 Memory, 103 Bus.

Claims

1. A power conversion unit connected between the power system and the load, which performs power conversion between the power system and the load, The system comprises a control unit for controlling the power conversion unit, The control unit, Using a correlation between the output active power of the power conversion unit and the reactive power command value that suppresses voltage fluctuations at the power source side position, which is closer to the power source of the power system than the connection point with the power system, derived in advance by simulation or calculation using an equivalent circuit that simulates the electrical characteristics of the power system, The reactive power command value corresponding to the output active power of the power conversion unit is determined, and the power conversion unit is controlled based on the determined reactive power command value. A power conversion device characterized by the following features.

2. The control unit, The reactive power command value is determined by using the active power on the load side as the output active power. The power conversion device according to feature 1.

3. The control unit, The system has a table associated with a reactive power command value that suppresses voltage fluctuations at the power supply side for each output active power with a different value, and the reactive power command value that controls the power conversion unit is determined using the table. The power conversion device according to feature 1 or 2.

4. The control unit, The reactive power command value for controlling the power converter is determined based on the calculation result of a formula that calculates a reactive power command value from the output active power of the power converter. The power conversion device according to feature 1 or 2.

5. The control unit, The reactive power command value for controlling the power conversion unit is determined based on the reactive power command value that suppresses voltage fluctuations at the power supply side location and the reactive power command value that suppresses voltage fluctuations at the interconnection point. The power conversion device according to feature 3.

6. The power conversion unit is A first power converter that converts AC power supplied from the aforementioned power system to DC power and converts DC power back to AC power and supplies it to the aforementioned power system, The system comprises a second power converter that converts DC power supplied from the first power converter into AC power and converts AC power supplied from the load into DC power and supplies it to the first power converter, The control unit, Based on the determined reactive power command value, the first power converter is controlled. The power conversion device according to feature 1 or 2.

7. Based on the output active power of a power conversion unit connected between the power system and the load, which performs power conversion between the power system and the load, Using a correlation between the output active power and a reactive power command value that suppresses voltage fluctuations at a power source-side position, which is closer to the power source of the power system than the connection point of the power system, derived in advance by simulation or calculation using an equivalent circuit that simulates the electrical characteristics of the power system, A determination step for determining the reactive power command value corresponding to the output active power, The control step includes controlling the power conversion unit based on the reactive power command value determined in the determination step. A control method characterized by the following:

8. Based on the output active power of a power conversion unit connected between the power system and the load, which performs power conversion between the power system and the load, Using a correlation between the output active power and a reactive power command value that suppresses voltage fluctuations at a power source-side position, which is closer to the power source of the power system than the connection point of the power system, derived in advance by simulation or calculation using an equivalent circuit that simulates the electrical characteristics of the power system, A determination step for determining the reactive power command value corresponding to the output active power, A control step in which the computer controls the power conversion unit based on the reactive power command value determined in the determination step. A control program characterized by the following features.

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