Power converter system

Abstract

Power converter system (50) comprising: at least one power converter device (10) with a converter (2a) for converting alternating current power into direct current power, a first voltage sensor (5) for obtaining a direct current voltage generated on a direct current side of the converter, and a control unit (3) for controlling an operating state of the converter; and a voltage transformer (1) with a primary winding (1a) connected to an alternating current power supply, at least one secondary winding (1b), and a tertiary winding (1c) connected to a second voltage sensor (6), wherein the at least one secondary winding is connected to the at least one power converter device in a one-to-one ratio, wherein the control unit features: a phase calculation unit (30) for calculating a reference phase from a value obtained by the second voltage sensor; an active current command value calculation unit (321, 322) for calculating an active current command value on the basis of a deviation of a DC voltage command value from the DC voltage obtained by the first voltage sensor; a first reactive current command value calculation unit (324) for receiving the active current command value and a first coefficient as a proportionality coefficient, wherein the first coefficient is determined by coupled inductances of the voltage transformer and a received voltage of the voltage transformer, and for calculating a first reactive current command value proportional to a square of the active current command value, by using the first coefficient; and a voltage command value calculation unit (34; 35) for calculating an AC voltage command value based on the reference phase, the active current command value and the first reactive current command value.

Description

Area

[0001] The present invention relates to a power converter system installed on an electric vehicle for converting an AC power output from an AC power input into a DC power output. background

[0002] Typically, an electric vehicle is configured to draw power from overhead power lines through a power collector, utilize the drawn power, and drive a motor via a power converter device to propel the electric vehicle. Specifically, an electric vehicle receiving power from an AC power supply typically employs a scheme for supplying power to a motor to propel the electric vehicle, via a voltage transformer that steps down an overhead line voltage, a converter that converts the AC power to DC power, and an inverter that converts the DC power to AC power. Therefore, the term "electric vehicle" will refer to an electric vehicle receiving power from an AC power supply.Additionally, a device that includes a voltage transformer, a converter, an inverter and a motor is referred to as a "propulsion control system".

[0003] An electric vehicle's voltage transformer has a primary winding connected to an overhead power line, a secondary winding connected to a converter, and a tertiary winding connected to other electrical equipment. Of these windings, the secondary winding is directly connected to the converter, and two or more secondary windings are often provided. Additionally, the number of windings typically decreases in order from primary to secondary to tertiary. This means the voltage decreases with each subsequent winding. Note that the primary winding is called the high-voltage winding, and the secondary and tertiary windings are called low-voltage windings.

[0004] To control the converter, information about the overhead line voltage is required. Note that in some cases, a voltage sensor for obtaining the overhead line voltage is installed on a tertiary winding of a voltage transformer. In such a configuration, a value obtained from the voltage sensor is converted into a turns ratio of the voltage transformer and used to control the converter. Connecting the voltage sensor to the tertiary winding allows the use of a voltage sensor with a lower test voltage rating. A configuration of such a power converter system is described, for example, in publication JP 2005 - 304 156 A, which is referenced below.

[0005] Publication JP 2017-188990A describes an effective current command value generator that produces an effective current command value corresponding to the effective power to be supplied by the power converter to the load resistance. An initial reactive current command value, calculated based on the difference between the target overhead line voltage and the actual overhead line voltage, is adjusted by at least the effective current command value. That is, it is adjusted to a value proportional to the effective current command value. Furthermore, a reactive current command setting value, which is the adjusted value, is limited by a limiter circuit so that it does not exceed an upper limit and is output as the reactive current command value.

[0006] The publication JP H09-135580A shows that in a compensation current calculator, a tertiary winding current detected by a current detector is multiplied by the ratio of the secondary and tertiary windings in terms of the number of turns. The reactive distributed current and the harmonic current at the tertiary winding are calculated using a reactive distributed current calculator and a harmonic current calculator. These reactive distributed currents and harmonic currents are added by an adder to obtain a compensation current. A compensation distributed current command value is subtracted by a subtractor to obtain an AC command value. Then, a deviation value from an AC current detected by a current detector is calculated by a subtractor to obtain a control signal in a current controller 88.In a voltage divider, the AC voltage detected by a current detector is divided by the DC current to calculate a control signal. In a subtractor, a control signal is subtracted from the control signal to obtain a modulation signal. A pulse signal is then generated by a PWM control circuit to control a converter.

[0007] Publication JP 2005 - 073 345 A discloses an electric train control unit comprising a converter; a VVVF inverter coupled to the DC side of the converter; a plurality of main conversion devices consisting of a current device sensing a current on the AC side of the converter; and a voltage control device regulating a converter output voltage so that a current command value is calculated such that the capacitor voltage of a filter circuit is brought to a prescribed value corresponding to a current value sensed by the current device; a voltage sensing device for sensing the voltage of an overhead contact line; and an invalid current command calculation device for calculating an invalid current command based on the contact line voltage sensed by the voltage sensing device.The current command is corrected exclusively with the invalid current command calculated by the invalid-current-command calculation device. Brief description of the technical problem

[0008] For the voltage transformer of the electric vehicle described above, three or more windings sharing magnetic paths exhibit magnetic coupling between all the windings. Therefore, a current flowing in one winding influences the voltage induced by another winding. More precisely, the output of the voltage sensor connected to the tertiary winding changes depending on the amount of power required by the transducers connected to the secondary winding.As a result, a difference occurs between a true overhead line voltage and an overhead line voltage obtained from a value of the voltage sensor, causing a problem of failure to control a power factor of the propulsion control from the overhead line power line, that is, a power factor on the primary side of the voltage transformer, as instructed by a command value from a control of the converter.

[0009] Patent literature 1 teaches a technique for intentionally causing a converter to operate in such a way that its power factor is less than 1. More precisely, patent literature 1 teaches a technique for causing a converter to operate by carrying a reactive current in such a way as to avoid fluctuations in the received voltage received by the voltage transformer. Unfortunately, such a technique does not account for the difference between the true overhead line voltage and the overhead line voltage obtained from the voltage sensor reading. Furthermore, the technique does not guarantee that the actual power factor is controlled as instructed by a command value from the converter's control system.

[0010] The present invention was made in view of the foregoing and it is therefore an object to provide a power converter system that is capable of controlling a power factor on a primary side of a voltage transformer in such a way that the power factor is a command value, even in a case where a voltage sensor is installed on a low-voltage winding of the voltage transformer in order to obtain an overhead line voltage. Solution to the problem

[0011] To solve the aforementioned problems and achieve the objective, a power converter system according to the present invention comprises a power converter device and a voltage transformer. The power converter device includes a converter for converting alternating current power into direct current power, a first voltage sensor for obtaining a direct current voltage generated on a direct current side of the converter, and a control unit for controlling the operating state of the converter. The voltage transformer has a primary winding connected to an alternating current power supply, a secondary winding, and a tertiary winding connected to a second voltage sensor. The control unit includes a phase calculation unit for calculating a reference phase from a value obtained by the second voltage sensor.The control unit also includes an active current command value calculation unit for calculating an active current command value based on a deviation of a DC voltage command value from the DC voltage obtained from the first voltage sensor. The control unit further includes a first reactive current command value calculation unit to receive the active current command value and a first coefficient as a proportionality coefficient, where the first coefficient is determined by the coupled inductances of the voltage transformer and a received voltage from the voltage transformer, and to calculate a first reactive current command value proportional to the square of the active current command value by using the first coefficient.The control unit also includes a voltage command value calculation unit for calculating an AC voltage command value based on the reference phase, the active current command value and the first reactive current command value. Advantageous effects of the invention

[0012] A power converter system according to the present invention produces an effect such that a power factor on a primary side of a voltage transformer can be controlled in such a way that the power factor is a command value, even in a case where a voltage sensor is installed on a low-voltage winding of the voltage transformer in order to obtain an overhead line voltage. Brief description of drawings Fig. Figure 1 shows a configuration diagram of an electric vehicle drive system with a power converter system according to a first embodiment. Fig. Figure 2 shows a schematic diagram illustrating an example of a configuration of a main part of the power converter system, which is located in Fig. 1 is shown. Fig. Figure 3 shows a first vector diagram to explain an operating principle of a device in the Fig. 1 and Fig. 2 converters shown. Fig. Figure 4 shows a second vector diagram to explain the operating principle in the Fig. 1 and Fig. 2 converters shown. Fig. Figure 5 shows a block diagram illustrating an example of a basic configuration of a control unit used in the Fig. 1 and Fig. 2 is shown. Fig. Figure 6 shows a vector diagram relating to a current command value when the control unit, which is in Fig. As shown in section 5, it is working. Fig. Figure 7 shows a block diagram illustrating an example of a basic configuration of a control unit used in the Fig. 1 and Fig. 2 is shown, which is different from the one in Fig. 5 is. Fig. Figure 8 shows a diagram representing an equivalent circuit that expresses a voltage transformer located in the Fig. 1 and Fig. 2 is shown, by using an ideal voltage transformer and coupled inductors. Fig. Figure 9 shows a vector diagram to illustrate a phase difference between an instantaneous current command that is fed into the control unit. Fig. 5 or in Fig. 7 can occur and a converted secondary operating voltage. Fig. Figure 10 shows a graph representing time waveforms of a voltage obtained from a sensor, a converted secondary operating voltage, and an alternating current when the phase difference, which is in Fig. 9 is shown, occurs. Fig. Figure 11 shows a first vector diagram to explain a control technique according to the first embodiment. Fig. Figure 12 shows a graph representing time waveforms of a voltage obtained from a sensor, a converted secondary operating voltage and an alternating current when the control technology according to the first embodiment is used. Fig. Figure 13 shows a second vector diagram to explain the control technology according to the first embodiment. Fig. Figure 14 shows a block diagram illustrating an example of a configuration of a current command value calculation unit according to the first embodiment. Fig. Figure 15 shows a block diagram that represents an example of a hardware configuration for implementing the computational functions of the control unit in the first embodiment. Fig. Figure 16 shows a block diagram that represents another example of a hardware configuration implementing the computational functions of the control unit in the first embodiment. Fig. Figure 17 shows a block diagram illustrating an example of a configuration of the current command value calculation unit according to the first embodiment, as described in Figure 17. Fig. 14 different ones. Fig. Figure 18 shows a first vector diagram to explain a control technique according to a second embodiment. Fig. Figure 19 shows a block diagram illustrating an example of a configuration of a current command value calculation unit according to the second embodiment. Fig. Figure 20 shows a block diagram illustrating an example of a configuration of the current command value calculation unit according to the second embodiment, which differs from the one in Fig. 19 is. Fig. Figure 21 shows a block diagram illustrating an example of a configuration of a main part of a drive control system according to a third embodiment. Fig. Figure 22 shows a diagram representing an equivalent circuit that expresses a voltage transformer located in Fig. 21 is shown, by using an ideal voltage transformer and coupled inductors. Fig. Figure 23 shows a block diagram illustrating an example of a configuration of a current command value calculation unit according to the third embodiment. Fig. Figure 24 shows a block diagram illustrating an example of a configuration of a current command value calculation unit according to a fourth embodiment. Description of embodiments

[0013] A power converter system according to certain embodiments of the present invention is described in detail below with reference to the drawings. It should be noted that the present invention is not limited to the embodiments described below. First embodiment.

[0014] Fig. Figure 1 shows a configuration diagram of an electric vehicle drive system 100 with a power converter system 50 according to the first embodiment. Fig. Figure 1 of the electric vehicle drive system 100 comprises a supply system 110 and a propulsion device 60, which performs propulsion control on an electric vehicle (not shown). The supply system 110 provides an AC power supply. The supply system 110 includes a power supply installation 106, which generates AC power, and a power line 108 for supplying the AC power to the propulsion device 60.

[0015] The propulsion device 60 comprises the power converter system 50 and a load 120. The power converter system 50 converts the alternating current power received from the supply system 110 into direct current power and supplies the direct current power to the load 120. The power converter system 50 comprises a voltage transformer 1 and a power converter device 10. The voltage transformer 1 reduces a received voltage and supplies the resulting voltage to the power converter device 10.

[0016] The power converter device 10 comprises a converter 2a, a capacitor 2b, and a control unit 3. The converter 2a is a pulse-width modulation (PWM) converter that converts AC power to DC power and vice versa. The converter 2a converts AC power supplied by the power supply system 110 into DC power via the voltage transformer 1 and supplies the DC power to the load 120. The capacitor 2b is a smoothing capacitor that smooths the output of the converter 2a.

[0017] One side of the converter 2a, on which the voltage transformer 1 is located, is referred to as the "AC side," and the other side of the converter 2a, on which the load 120 is located, is referred to as the "DC side." The control unit 3 generates PWM signals to perform PWM control on the converter 2a. The control unit 3 controls the operating state of the converter 2a by means of the PWM signals. More precisely, the control unit 3 controls the voltage on the DC side of the converter 2a. The control unit 3 also controls the current flowing into and out of the AC side of the converter 2a. Therefore, the voltage on the DC side of the converter 2a is referred to as the "DC voltage of the converter 2a" or simply as the "DC voltage."Additionally, the current flowing into and out of the AC side of converter 2a is referred to as the "AC current of converter 2a" or simply as an "AC current." Similarly, the voltage on the AC side of converter 2a is referred to as the "AC voltage of converter 2a" or simply as an "AC voltage." Note that many well-known documents exist on techniques for generating PWM signals, and therefore a detailed description of these techniques is omitted here.

[0018] The load 120 comprises an inverter 120a and a motor 120b. The inverter 120a converts a DC power output from the converter 2a into AC power. The motor 120b is driven by the AC power obtained through the conversion at the inverter 120a. The motor 120b provides propulsion to the electric vehicle, which is not shown. Note that the number of motors 120b driven by one inverter 120a can be greater than one.

[0019] Additionally, while a single inverter 120a is connected to a single power converter device 10 in Fig. As shown in Figure 1, a single power converter device 10 can be configured to supply power to a plurality of inverters 120a. Alternatively, a plurality of power converter devices 10 can be configured to supply power to a single inverter 120a. Note that a case where the number of power converter devices 10 is greater than one is described later.

[0020] Fig. Figure 2 shows a schematic diagram illustrating an example of a configuration of a main part of the power converter system 50. In addition to the voltage transformer 1 and the power converter device 10, which are located in Fig. The figure shown in 1 represents the Fig. 2 represents a current sensor 4, a voltage sensor 5, which is a first voltage sensor, and a voltage sensor 6, which is a second voltage sensor.

[0021] As in Fig. As shown in Figure 2, the voltage transformer 1 has a primary winding 1a, a secondary winding 1b, and a tertiary winding 1c. The primary winding 1a is connected to the power line 108, the secondary winding 1b is connected to the converter 2a, and the tertiary winding 1c is connected to the voltage sensor 6. While the number of power converter devices 10 and the number of secondary windings 1b are each one, for the sake of simplicity, in Fig. 2. The number of power converter devices 10 and the number of secondary windings 1b can be two or more. However, the power converter devices 10 and the secondary windings 1b are connected to each other in a one-to-one ratio.

[0022] The current sensor 4 obtains a current value of one alternating current i sof the converter 2a. The voltage sensor 5 obtains a voltage value of a DC voltage Ed of the converter 2a. The voltage sensor 6 obtains a voltage value of a voltage v^s induced in the tertiary winding 1c. The respective values ​​obtained by the current sensor 4 and the voltage sensors 5 and 6 are entered into the control unit 3. Note that "v^" in the expression "v^s" is a substitute for a character "v" with the hat symbol "^" on it. In this description, this substitute is used except when the expression is inserted as an image. Note that the value obtained by the voltage sensor 6 is equivalent to a secondary voltage converted in the voltage transformer 1 using a turns ratio of the secondary winding 1b and the tertiary winding 1c. The secondary voltage used here is a voltage induced in the secondary winding 1b.The winding ratio is also a voltage ratio. Accordingly, "v^s" is referred to as a "sensor-detected voltage".

[0023] Next, an operating principle of converter 2a will be described with reference to the Fig. 3 and Fig. 4 described. Fig. Figure 3 is a first vector diagram to explain the operating principle of the converter, which is located in Fig. 1 and Fig. 2 is shown. Fig. Figure 4 is a second vector diagram to explain the operating principle of the device in the Fig. 1 and Fig. 2 of the converter shown. Note that a state in which positive power is transferred from the AC side to the DC side of converter 2a is defined as a "power drive", and a state in which positive power is transferred from the DC side to the AC side is defined as a "regeneration". Based on these definitions, the direction in which the AC current i sof the converter 2a, which is obtained through the current sensor 4, into which the current flows, is defined as positive.

[0024] Fig. Figure 3 represents the ratio between a voltage vector and a current vector in a steady state when the converter 2a consumes power with a power factor of 1. Fig. 3 represents “i s “The alternating current of converter 2a, “xl” represents a leakage reactance of voltage transformer 1, and “vc” represents the alternating current voltage of converter 2a. Voltage transformer 1 receives from power line 108 and converts the received voltage into an equivalent value to a secondary voltage, using a turns ratio of the primary winding 1a and the secondary winding 1b in voltage transformer 1, thereby providing “vs”. “vs” is referred to as a “converted secondary operating voltage”.

[0025] Note that in reality, a resistance component is present in the voltage transformer 1 in addition to the leakage reactance xl. The sum of the resistance component and the leakage reactance xl is called the "leakage impedance." The resistance component in the leakage impedance is sufficiently small compared to a reactance component. Therefore, for the sake of simplicity, the resistance component is ignored in the following description.

[0026] As in Fig. Figure 3 shows the alternating current i in the power test and in the steady state with a power factor of 1. s and the converted secondary operating voltage vs in phase with each other. A voltage drop across the leakage reactance xl of voltage transformer 1 can be expressed as "jxlis". "j" is an imaginary unit and the voltage drop jxlis has a phase that is 90 degrees out of phase with the alternating current i. sand precedes the converted secondary operating voltage vs. Note that if there is a voltage difference between the converted secondary operating voltage vs and the AC voltage vc of converter 2a, the leakage reactance xl is affected, thereby increasing the AC current i. s is generated. Therefore, the result of a vector addition of the AC voltage vc of converter 2a and the voltage drop jxlis via the leakage reactance xl is equal to the converted secondary operating voltage vs. More precisely, the converted secondary operating voltage vs, the AC voltage vc, and the voltage drop jxlis satisfy the equation of vs=vc+jxlis.

[0027] Additionally, it Fig. 4. The ratio between the voltage vector and the current vector in a steady state when the converter 2a regenerates power with a power factor of 1. In Fig. 4 are the alternating current i sand the converted secondary operating voltage vs in opposite phases to each other. Note that the voltage drop jxlis across the leakage reactance xl in the voltage transformer 1 has a phase that is 90 degrees from the alternating current i. s leads the converted secondary operating voltage but lags behind it by 90 degrees. The ratio vs = vc + jxlis is satisfied in the vector diagram of Fig. 3 and a result of a vector addition of the AC voltage vc and the voltage drop jxlis via the leakage reactance is equal to the converted secondary operating voltage vs.

[0028] Therefore, the vector diagrams of the Fig. 3 and Fig. 4, that either one or both of the amplitude and phase of the alternating current voltage vc are adjusted in order to thereby determine the alternating current i s to control in such a way that the alternating current i s can exhibit any given amplitude and any given phase.

[0029] Next, a basic configuration and operation of control unit 3, which is located in Fig. 1 and Fig. 2 is shown, with reference to the Fig. 5 and Fig. 6 described. Fig. Figure 5 shows a block diagram illustrating an example of a basic configuration of the control unit 3, which is used in the Fig. 1 and Fig. 2 is shown. Fig. Figure 6 shows a vector diagram relating to a current command value when the control unit, which is in Fig. 5 is shown, is in operation.

[0030] The control unit 3, which is in Fig. Figure 5 shows a phase calculation unit 30, a current command value calculation unit 32, a voltage command value calculation unit 34, and a switching command generation unit 36. The operation of each of the units is explained below.

[0031] The phase calculation unit 30 generates a voltage phase θ based on the sensor-detected voltage v^s. The voltage phase θ is a reference phase for generating an instantaneous current command value is*, which will be described later. Hereafter, the voltage phase will be referred to as a "reference phase." The reference phase θ is input into the voltage command value calculation unit 34. Note that various known schemes have been proposed for configuring the phase calculation unit 30, and a detailed description of these is therefore omitted here.

[0032] The current command value calculation unit 32 is a component that calculates an active current command value Ip and a reactive current command value Iq based on a DC voltage command value Ed*, the DC voltage Ed obtained from the voltage sensor 5, and a power factor angle command value φ. More precisely, as in Fig. As shown in Figure 5, the current command value calculation unit 32 comprises a subtractor 321, a voltage control unit 322, a tangent value calculation unit 336, and a multiplier 323. The DC voltage command value Ed* is a command value for controlling the DC voltage Ed so that the DC voltage Ed has a desired value.

[0033] The subtractor 321 calculates a DC voltage deviation, which is the deviation of the DC voltage command value Ed* from the DC voltage Ed. The voltage control unit 322 calculates the active current command value Ip based on an output from the subtractor 321. The active current command value Ip is input to the voltage command value calculation unit 34 and the multiplier 323. The subtractor 321 and the voltage control unit 322 define an active current command value calculation unit.

[0034] Additionally, the tangent value calculation unit 336 generates a tangent value, which is a tangent to the power factor angle command value φ. The multiplier 323 multiplies the active current command value Ip by the output of the tangent value calculation unit 336. The output of the multiplier 323 is the reactive current command value Iq, which is input into the voltage command value calculation unit 34. The tangent value calculation unit 336 and the multiplier 323 define a reactive current command value calculation unit.

[0035] Note that a proportional-integral (PI) compensator is frequently used as the voltage control unit 322. Additionally, given the power factor angle command value φ, the ratio between the active current command value Ip and the reactive current command value Iq to achieve a desired power factor is expressed by the following formula. [Formula 1] Iq=Ip tan ϕ

[0036] Therefore, the current command value calculation unit 32 calculates in Fig. 5, which is the reactive current command value Iq by multiplying the active current command value Ip by tan φ, through a tangent value of the power factor angle command value φ. In the case of the Fig. 5. If the power factor angle command value φ is positive, the reactive current command value Iq is also positive, and Iq represents a leading reactive current. If the power factor angle command value φ is negative, the reactive current command value Iq is also negative, and Iq represents a lagging reactive current. When the reactive current command value Iq is determined in this way, and the instantaneous current command value is* is calculated such that the power factor of the AC power follows a desired value, the instantaneous current command value is* is described below. To ensure that a quantity of reactive power follows a desired value, the reactive current command value Iq can be calculated directly by other means, without using the power factor angle command value φ.

[0037] Next, the voltage command value calculation unit 34 is described. The voltage command value calculation unit 34 is a component that calculates the instantaneous current command value is* based on the active current command value Ip, the reactive current command value Iq, and the reference phase θ. The voltage command value calculation unit 34 is also a component that calculates an AC voltage command value vc* based on the instantaneous current command value is*, and the AC current is obtained from the current sensor 4. The AC voltage command value vc* is a command value for a voltage that the converter 2a is to output to the AC side. More precisely, as in Fig. As shown in Figure 5, the voltage command value calculation unit 34 has a sine value calculation unit 341, a cosine value calculation unit 342, multipliers 343 and 344, an adder 345, a subtractor 346 and a current control unit 347.

[0038] The sine function calculation unit 341 calculates a sine value of the reference phase θ, and the cosine function calculation unit 342 calculates a cosine value of the reference phase θ. The multiplier 343 multiplies the active current command value Ip by the sine value of the reference phase θ. The active current command value Ip is an output of the current command value calculation unit 32. The sine value of the reference phase θ is an output of the sine function calculation unit 341. The multiplier 344 multiplies the reactive current command value Iq by the cosine value of the reference phase θ. The reactive current command value Iq is the output of the current command value calculation unit 32. The cosine value of the reference phase θ is the output of the cosine function calculation unit 342. The adder 345 adds Ipsinθ and Iqcosθ. Ipsinθ is the output of multiplier 343 and Iqcosθ is the output of multiplier 344. The output of adder 345 is the instantaneous current command value is*.The instantaneous current command value is* is a command value of a current that is to flow to the AC side of the converter 2a.

[0039] Note that the active current command value Ip and the reactive current command value Iq are both DC quantities, while the instantaneous current command value is* is an AC quantity. For the configuration of the Fig. 5 is a product of the active current command value Ip and sinθ, which is the sine value of the reference phase θ, an AC quantity that is in phase with the sensor-acquired voltage v^s. A product of the reactive current command value Iq and cosθ, which is the cosine value of the reference phase θ, is an AC quantity that is 90 degrees out of phase with the sensor-acquired voltage v^s. For the configuration of the Fig. 5 is the reference phase θ based on the sine value of the sensor-acquired voltage v^s. The sensor-acquired voltage v^s and the instantaneous current command value is* therefore satisfy the equation shown in the vector diagram of the Fig. 6 ratios shown.

[0040] The instantaneous current command value is* is entered into subtractor 346. Subtractor 346 calculates a deviation of the instantaneous current command value is* from the alternating current i. s The alternating current i s is an alternating current of the converter 2a, which is obtained by the current sensor 4. The current control unit 347 amplifies the deviation of the instantaneous current command value is* from the alternating current i. s and outputs the amplified signal as the AC voltage command value vc* to the switching command generation unit 36. Note that a proportional (P) compensator or a PI compensator is often used as the current control unit 347.

[0041] The switching command generation unit 36 ​​generates a switching command sw* based on the AC voltage command value vc*. The switching command sw* is a PWM signal for performing PWM control on the converter 2a. Note that a known technique is used to generate the switching command sw*, and a detailed description of this technique is therefore omitted here.

[0042] Note that the voltage command value calculation unit 34, which is in Fig. 5, can be replaced, for example, by a voltage command value calculation unit 35, which is shown in Fig. 7 is shown. Fig. Figure 7 shows a block diagram illustrating an example of a basic configuration of control unit 3, which is described in Figure 7. Fig. 1 and Fig. 2 shown, shows, which differs from the Fig. 5 is. In Fig. 7 are components that are the same as or corresponding to those of the Fig. 5 are represented by the same reference symbols.

[0043] The configuration of Fig. 7 differs from the configuration of Fig. 5 in converting an actual current into a direct current quantity, different from the configuration of the Fig. 5, which converts the current command value into the alternating current quantity. More precisely, as in Fig. As shown in Figure 7, the voltage command value calculation unit 35 comprises a rotation coordinate transformation unit 351, subtractors 352 and 353, current control units 354 and 355, and a steady-state coordinate transformation unit 356. Note that, like the voltage command value calculation unit 34, which is shown in Figure 7, the voltage command value calculation unit 355 comprises a rotation coordinate transformation unit 351, subtractors 352 and 353, current control units 354 and 355, and a steady-state coordinate transformation unit 356. Fig. Figure 5 shows the voltage command value calculation unit 35, which is in Fig. Figure 7 is shown, configured to set the AC voltage command value vc* based on the active current command value Ip, the reactive current command value Iq, the reference phase θ and the AC current i sto calculate the voltage obtained from current sensor 4. The AC voltage command value vc* is a voltage that converter 2a should output to the AC side.

[0044] The rotational coordinate transformation unit 351 uses the reference phase θ to transform the alternating current i s The value is converted to a value on the rotational coordinates in order to calculate an actual active current Ip' and an actual reactive current Iq'. The actual active current Ip' is a component that is in phase with the sensor-sensed voltage v^s. The actual reactive current Iq' is a component that is 90 degrees out of phase with the sensor-sensed voltage v^s.

[0045] Subtractor 352 calculates the deviation of the active current command value Ip from the actual active current Ip'. The active current command value Ip is an output of the current command value calculation unit 32. The actual active current Ip' is an output of the rotation coordinate transformation unit 351. Additionally, subtractor 353 calculates the deviation of the reactive current command value Iq from the actual reactive current Iq'. The reactive current command value Iq is an output of the current command value calculation unit 32. The actual reactive current Iq' is an output of the rotation coordinate transformation unit 351.

[0046] The current control unit 354 amplifies the deviation of the active current command value Ip from the actual active current Ip' and outputs the amplified signal as a p-axis voltage command value vp* to the steady-state coordinate transformation unit 356. Additionally, the current control unit 355 amplifies the deviation of the reactive current command value Iq from the actual reactive current Iq' and outputs the amplified signal as a q-axis voltage command value vq* to the steady-state coordinate transformation unit 356.

[0047] The stationary coordinate transformation unit 356 uses the reference phase θ to transform the p-axis voltage command value vp* and the q-axis voltage command value vq* into a value on the stationary coordinates and outputs the value obtained by the transformation as the AC voltage command value vc* to the switching command generation unit 36.

[0048] In a case where the AC power is single-phase, instantaneous space vectors of voltage and current cannot be defined. Therefore, additional computational processes are necessary for the mutual transformation of rotational and stationary coordinates. More precisely, for a rotational coordinate transformation of the AC current i s , jis, which is a component with one phase that is 90 degrees away from the alternating current i s , anticipates, is calculated in advance, and the rotational coordinate transformation is applied to the alternating currents i s and performed. If a transformation matrix represents this process by C, the transformation matrix C is expressed by the following formula. [Formula 2] C=(sin θcosθcosθ−sin θ)

[0049] It should be recognized that the transformation matrix of formula (2) varies depending on the way the reference phase θ is defined.

[0050] Additionally, using the transformation matrix C of the formula (2) mentioned above, the actual active current Ip' and the actual reactive current Iq' described above are expressed by the following formula. [Formula 3] (Ip'Iq')=C×( isjis)

[0051] Additionally, the AC voltage command value vc* is expressed by the following formula using the transformation matrix C of formula (2). [Formula 4] (vc*jvc*)=C−1×(Vp*Vq*)

[0052] Next, the influence of voltage transformer 1 on the control will be discussed with regard to the Fig. 8 to 10 described. Fig. Figure 8 shows a diagram representing an equivalent circuit that includes the voltage transformer found in Fig. 1 and Fig. 2 is represented by the use of an ideal voltage transformer and coupled inductors. Fig. Figure 9 shows a vector diagram to illustrate a phase difference between the instantaneous current command value is*, which is entered into the control unit. Fig. 5 or Fig. 7 can occur and the converted secondary operating voltage vs. Fig. Figure 10 shows a graph representing the time waveforms of the sensor-acquired voltage v^s, the converted secondary operating voltage vs, and the alternating current is, when the phase difference is in Fig. 9 is shown, occurs.

[0053] In Fig. Figure 8 represents the voltage transformer 1 as an ideal voltage transformer 70 and coupled inductances 74. The coupled inductances 74 represent a leakage inductance between a high-voltage winding and a low-voltage winding, and a magnetic coupling between the low-voltage windings and the voltage transformer 1. The leakage inductance is also referred to as leakage reactance.

[0054] In Fig. In 8, “v1” represents a primary voltage, “v2” represents a secondary voltage, “v3” represents a tertiary voltage, “i1” represents a primary current, “i2” represents a secondary current, and “i3” represents a tertiary current. More precisely, the primary voltage v1 is a voltage applied to the primary winding, and the primary current i1 is the current flowing through the primary winding. Additionally, the secondary voltage v2 is a voltage induced by the secondary winding, the secondary current i2 is a current flowing through the secondary winding, the tertiary voltage v3 is a voltage induced by the tertiary winding, and the tertiary current i3 is a current flowing through the tertiary winding. Note that for simplicity, the primary winding can be referred to as the “high-voltage winding,” and the secondary and tertiary windings together can be referred to as the “low-voltage windings.”Additionally, "n2" represents a turns ratio of the secondary winding to the primary winding, and "n3" represents a turns ratio of the tertiary winding to the primary winding. Note that if the number of turns of the primary winding is expressed by "1" as shown, the turns ratio n2 and the turns ratio n3 are real numbers equal to or greater than 0 and less than 1.

[0055] Note that in the equivalent circuit in Fig. 8 circuit equations of the following formulas are satisfied. [Formula 5] il=n2 i2+n3 i3 [Formula 6] (n2n3)vl−(v2v3)=j(x22x23x32x33)×(i2i3)

[0056] A coefficient matrix on the right-hand side of formula (6) is called a "reactance matrix". The reactance matrix is ​​a parameter that expresses coupled inductances 74 in terms of their impedances. Diagonal terms of the reactance matrix are terms arising from self-inductances of the low-voltage windings, and off-diagonal terms are terms arising from mutual inductances of the low-voltage windings. Additionally, the reactance matrix is ​​a symmetric matrix. A second version of formula (6) is developed, providing the following formula. [Formula 7] v3=n3 vl−j(x32 i2+x33 i3)

[0057] Formula (7) shows that the tertiary voltage v3 changes depending on the current of the low-voltage winding.

[0058] Additionally, formula (7) is deformed, resulting in the following formula. [Formula 8] n2 v1=(n2 / n3)v3+j(n2 / n3)(x32 i2+x33 i3)

[0059] Note that in the configuration the Fig. 2. The load on the tertiary winding 1c is only the voltage sensor 6, and the current flowing through the voltage sensor 6 is small. For this reason, it can be assumed that the tertiary current i3 is zero, i3=0. Although an electric vehicle may have another load, such as an auxiliary power supply, to which the tertiary winding 1c may be connected, its power capacity is smaller than that of the secondary winding's converter in most cases. Therefore, the assumption that the tertiary current i3 can be ignored, i.e., that the tertiary current is zero (i3=0), is reasonable and appropriate.

[0060] Additionally, the left-hand side of formula (8) is a value obtained by converting the primary voltage v1 into a secondary voltage, and this value is referred to as the converted secondary operating voltage vs and is defined as described above. Furthermore, the first term on the right-hand side is a value obtained by converting the value obtained by the voltage sensor 6 into a secondary voltage equal to the sensor-acquired voltage v^s. Because the secondary current i2 of the voltage transformer 1 is equal to the alternating current i s of converter 2a and the alternating current i s is controlled in such a way that the alternating current i s The instantaneous current command value is*. For this reason, it can be assumed that the current i2 is equal to is* (i2=is*). Furthermore, if a proportionality coefficient “(n2 / n3)x32” in the second term on the right-hand side is defined as “xm”, i.e., xm=(n2 / n3)x32, the following formula is obtained. [Formula 9] vs=v^s+j xm is ∗

[0061] Assuming that a control target has a power factor of 1 and the reactive current command value Iq is zero, the ratio in formula (9) can be expressed by the vector diagram of the Fig. 9. In Fig. 9. The instantaneous current command value is* is in phase with the sensor-acquired voltage v^s. Additionally, a phase difference angle δ exists between the sensor-acquired voltage v^s and the converted secondary operating voltage vs. Therefore, a phase difference corresponding to the phase difference angle δ is also generated between the instantaneous current command value is* and the converted secondary operating voltage vs.

[0062] In this case, time waveforms of the sensor-acquired voltage v^s, the converted secondary operating voltage vs, and the alternating current i are used. s as in the Fig. 10 shown. In Fig. 10 are the sensor-detected voltage v^s and the alternating current i s The primary voltage is shown in solid curves, and the converted secondary operating voltage is shown in a dashed curve. As shown in Fig. As shown in Figure 10, a phase difference corresponding to the phase difference angle δ is generated between the sensor-acquired voltage v^s and the converted secondary operating voltage vs. Additionally, as a result of the alternating current i s is controlled in such a way that the alternating current i s The instantaneous current command value is* follows, the alternating current i s in phase with the sensor-acquired voltage v^s. Therefore, a phase difference corresponding to the phase difference angle δ is also generated between the converted secondary operating voltage vs and the alternating current i. sThis means that a control target has a power factor of 1, but the power factor on the primary side of the voltage transformer 1 is not 1.

[0063] As described above, in the basic configuration, which is in Fig. 5 or Fig. As shown in Figure 7, the sensor-determined voltage v^s can have a phase different from that of the converted secondary operating voltage vs. This results in a problem: the power factor or reactive power quantity of the AC power on the primary side of the voltage transformer 1 is not provided as instructed by the control unit 3. A control technique of the first embodiment solves this problem by correcting the instantaneous current command value is*, as explained below.

[0064] Fig. Figure 11 shows a first vector diagram to illustrate a control technique in its first embodiment. First, as in Fig. As shown in Figure 11, an axis in phase with the sensor-acquired voltage v^s is defined as a p-axis, and an axis with a phase leading the p-axis by 90 degrees is defined as a q-axis. Next, the instantaneous current command value is* is resolved into a p-axis component ip and a q-axis component iq1', assuming that the instantaneous current command value is* is in phase with the converted secondary operating voltage vs. Note that the amplitude of the p-axis component ip corresponds to the active current command value Ip output from the current command value calculation unit 32 in the configuration of the control unit 3, which is shown in the Fig. 5 or Fig. Figure 7 is shown. Additionally, the amplitude of the q-axis component iq1' is redefined as a first reactive current command correction value Iq1'. If the vector diagram of the Fig. 11. When solved geometrically, the ratio between the active current command value Ip and the first reactive current command correction value Iq1' is expressed by the following formula. [Formula 10] Iq1'=xmI2p / |vs|2−(xmIp)2

[0065] Note that with k=xm / |vs|, formula (10) is expressed by the following formula. [Formula 11] Iq1'=kI2p / 1−(k Ip)2

[0066] In this case, the time waveforms of the sensor-acquired voltage v^s, the converted secondary operating voltage vs, and the alternating current i are s as in Fig. 12. Fig. Figure 12 shows a graph that displays time waveforms of the sensor-acquired voltage v^s, the converted secondary operating voltage vs, and the alternating current i. s This is the case when the control technology of the first embodiment is used.

[0067] According to Fig. 12. A phase difference corresponding to the phase difference angle δ is generated between the sensor-acquired voltage v^s and the converted secondary operating voltage vs. However, the instantaneous current command value is* is in phase with the converted secondary operating voltage vs, as shown in FIG. 11. Therefore, the alternating current i s controlled in such a way that the alternating current i s in phase with the converted secondary operating voltage vs in Fig. 12 is. Compared to the waveforms of the Fig. 10, the phase difference between the converted secondary operating voltage vs and the alternating current i s eliminated. Therefore, this means that the power factor on the primary side of the voltage transformer becomes 1 to 1.

[0068] Fig. Figure 13 shows a second vector diagram to explain the control technology according to the first embodiment. Fig. 13 presents a vector diagram as in Fig. 11. This applies in the case of regenerative operation with a power factor of 1. In the case of regenerative operation with a power factor of 1, the instantaneous current command value is* is in opposite phase to the converted secondary operating voltage vs, and the first reactive current command correction value Iq1' has a phase that lags the active current command value Ip by 90 degrees. In contrast, the ratio between the active current command value Ip and the first reactive current command correction value Iq1' is the same as in the case of the Fig. 11, which satisfies the ratio of formula (11).

[0069] Note that the sign of Iq1' that satisfies formula (11) is positive, independent of the sign of Ip, when k > 0. In other words, when xm > 0, the value of the first reactive power command correction value Iq1' is positive, regardless of whether driving or regeneration is taking place. Conversely, when xm < 0, the value of the first reactive power command correction value Iq1' is negative, regardless of whether driving or regeneration is taking place.

[0070] Note that formula (11), which involves calculating a square root and division, presents a computational burden that is not necessarily easy. With this in mind, a simplification of formula (11) is attempted. If a basic capacitance is represented by Sb, a basic voltage by |vs|, a basic impedance by Zb, and xm and Ip are expressed in a per-unit system by %x and %i respectively, the ratios Ip = (Sb / |vs|) × %i and xm = Zb × %x = (|vs|² / Sb) × %x are satisfied. These ratios are substituted into the denominator of formula (11), thus providing the following formula. [Formula 12] Iq1'=kI2p / 1−(%x)2(%i)2

[0071] On the right-hand side of formula (6), diagonal terms in the reactance matrix represent a few percent to a few tenths of a percent of the base capacity. Furthermore, terms outside the diagonal in the reactance matrix are typically still smaller than the diagonal terms. Therefore, (%x)² << 1 can be considered true in formula (12), and lq1' can be approximated as Iq1' ≈ kIp². Thus, as expressed by the following formula, the approximated first reactive current command correction value Iq1' is redefined as a first reactive current command value Iq1. [Formula 13] Iq1:=kI2p

[0072] As described above, the voltage command value calculation unit 34 can calculate the AC voltage command value vc* based on the first reactive current command value Iq1. Such a simple calculation accomplishes the task of controlling the power factor of the AC power on the primary side of the voltage transformer 1 such that the power factor is 1. The current command value calculation unit that achieves this function is as shown in Fig. 14 are shown, configured, for example. Fig. Figure 14 shows a block diagram illustrating an example of a configuration of the first current command value calculation unit according to the first embodiment. Fig. 14 are components that are the same as or corresponding to those of the Fig. 5 or Fig. 7 are designated by the same reference symbols.

[0073] The current command value calculation unit 32A, which is in Fig. Figure 14 shows a first reactive current command value calculation unit 324 instead of the tangent value calculation unit 336 and the multiplier 323 in the current command value calculation unit 32, which are shown in the Fig. 5 or Fig. 7 is shown. Fig. In section 14, the subtractor 321 and the voltage control unit 322 define an active current command value calculation unit 320. An active current command value Ip, calculated by the active current command value calculation unit 320, and a coefficient k, which is a first coefficient, are input into the first reactive current command value calculation unit 324. Note that the coefficient k is expressed as k = xm / |vs|, as described above. Additionally, the proportionality coefficient xm is a coefficient derived from the coupled inductances 74 of the voltage transformer 1. Furthermore, the converted secondary operating voltage |vs| is a value determined by the received voltage of the voltage transformer 1. Therefore, the coefficient k can be defined by the coupled inductances 74 of the voltage transformer 1 and the received voltage of the voltage transformer 1.

[0074] The first reactive current command value calculation unit 324 uses the coefficient k as a proportionality coefficient and calculates a first reactive current command value Iq1 that is proportional to the square of the active current command value Ip. The active current command value Ip and the first reactive current command value Iq1, calculated by the current command value calculation unit 32A, are input to the voltage command value calculation unit 34 or 35, which is located in Fig. 5 or Fig. Figure 7 is shown. The AC voltage command value vc* is then calculated based on the active current command value Ip and the first reactive current command value Iq1. The switching command sw* is generated based on the AC voltage command value vc* to control the operating state of converter 2a.

[0075] As described above, according to the first embodiment, the current command value calculation unit of a control unit calculates the first reactive current command value proportional to the square of the active current command value, using, as the proportionality coefficient, the coefficient k, which is determined by the coupled inductances of the voltage transformer and the voltage received by the voltage transformer. The current command value calculation unit then outputs the first reactive current command value, together with the active current command value, to the voltage command value calculation unit. Additionally, the voltage command value calculation unit calculates the AC voltage command value based on the reference phase, which is derived from the value obtained from the second voltage sensor, the active current command value, and the first reactive current command value.This makes it possible to control the power factor on the primary side of the voltage transformer in such a way that the power factor is a command value, even in a case where the second voltage sensor is installed on the tertiary winding of the voltage transformer in order to obtain an overhead line voltage.

[0076] Next, hardware configurations for implementing the calculation functions of the control unit 3 in the first embodiment are described with reference to the Fig. 15 and Fig. 16 described. Fig. Figure 15 is a block diagram that shows an example of a hardware configuration for implementing the computational functions of the control unit in the first embodiment. Fig. Figure 16 shows a block diagram that represents another example of a hardware configuration for implementing the computational functions of the control unit in the first embodiment.

[0077] As in Fig. Figure 15 shows that, to implement all or some of the calculation functions of the control unit 3 in the first embodiment by software, a configuration can be used with a processor 300 that performs a calculation, a memory 302 in which programs to be read by the processor 300 are stored and an interface 304 for signal input and output.

[0078] The processor 300 can be a computational device, such as a computing unit, a microprocessor, a microcomputer, a central processing unit (CPU), or a digital signal processor (DSP). Additionally, examples of memory 302 include volatile or non-volatile semiconductor memory such as random access memory (RAM), read-only memory (ROM), flash memory, erasable programmable ROM (EPROM), or electrical EPROM (EEPROM: registered trademark), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisc, and a digital versatile disk (DVD).

[0079] Memory 302 stores programs for implementing all or some of the calculation functions of the control unit 3. The processor 300 can perform PWM control on the converter 2a by providing and receiving necessary information via interface 304 and executing the programs stored in memory 302.

[0080] Alternatively, the processor can be 300 and the memory 302, which is in the Fig. 15 is shown, with processing circuits 303 as in Fig. Figure 16 is shown and can be replaced. The processing circuit 303 can be a single circuit, a composite circuit, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or combinations thereof.

[0081] The hardware configurations for implementing the computational functions of the control unit 3 in the first embodiment have been described above. Note that in a case where there is remaining computational capacity of the processor 300 and the memory 302 or the processing circuits 303, the configuration of the current instruction value calculation unit 32A, which is described in Fig. 14 is shown, which is in Fig. 17 can be changed. Fig. Figure 17 shows a block diagram illustrating an example of a configuration of the current command value calculation unit according to the first embodiment, which is described in the Fig. 14 different ones. Fig. 17 are components that are the same as or equivalent to those in Fig. 14 are designated by the same reference symbols.

[0082] A current command value calculation unit 32B, which is in Fig. Figure 17 further shows a first correction calculation unit 325 in the configuration of the Fig. 14. The active current command value Ip, which is calculated by the active current command value calculation unit 320, the coefficient k and the first reactive current command value Iq1 are calculated by the first reactive current command value calculation unit 324 and entered into the first correction calculation unit 325.

[0083] Note that if the newly defined first reactive current command value Iq1 is used by formula (13), formula (11) can be expressed by the following formula. [Formula 14] Iq1'=Iq1 / 1−(kIp)2

[0084] The first correction calculation unit 325 in Fig. 17 is a calculation unit that performs the calculation expressed by formula (14). More precisely, the first correction calculation unit 325 calculates a first reactive command correction value Iq1' based on the first reactive command value Iq1 output from the first reactive command value calculation unit 324 and the coefficient k, which is a proportionality coefficient. The first reactive command correction value Iq1' is a corrected value of the first reactive command value Iq1. The current command value calculation unit 32B then outputs the first reactive command correction value Iq1' to the voltage command value calculation unit 34 as the first reactive command value.

[0085] The active current command value Ip and the first reactive current command correction value Iq1', calculated by the current command value calculation unit 32B, are entered into the voltage command value calculation unit 34 or 35, which is located in Fig. 5 or Fig. Figure 7 is shown. The AC voltage command value vc* is then calculated based on the active current command value Ip and the first reactive current command correction value Iq1'. The switching command sw* is generated based on the AC voltage command value vc* to control the operating state of converter 2a.

[0086] The 32B current command value calculation unit provides improved accuracy in controlling the power factor, so that the power factor is a command value, compared to the 32A current command value calculation unit. Second embodiment

[0087] The first embodiment discloses that the magnitude of the reactive current to be output by the current command value calculation unit when the control target is a power factor of 1 is disclosed. In contrast, the power factor can be controlled so that it is a value other than 1, or reactive power can be intentionally generated for the purpose of, for example, stabilizing the operation of the converter under a light load or stabilizing the operating voltage in conjunction with an AC power supply. An explanation is given of how the current command value calculation unit calculates a reactive current so that the control unit controls the power factor or the amount of reactive power as intended.

[0088] Fig. Figure 18 shows a first vector diagram to illustrate a control technique according to a second embodiment. First, as in Fig. As shown in Figure 18, an axis in phase with the sensor-acquired voltage v^s is defined as a p-axis, and an axis with a phase leading the p-axis by 90 degrees is defined as a q-axis. Next, the instantaneous current command value is* is resolved into a p-axis component ip and a q-axis component iq3, assuming that the instantaneous current command value is* has a phase leading the converted secondary supply voltage vs by a power factor angle command value φ. The p-axis component ip has an amplitude corresponding to the active current command value Ip provided to the control unit 3. Additionally, the amplitude of the q-axis component iq3 is represented by Iq3. Furthermore, a phase difference angle, which is an angle between the converted secondary supply voltage vs and the sensor-acquired voltage v^s, is represented by δ.In this case, the amplitude of the q-axis component iq3 is expressed by the following formula. [Formula 15] Iq3=Ip×tan(δ+ϕ)=Ip(tan ϕ+k|is*| / cos ϕ)

[0089] Note that k in formula (15) is defined as k = xm / |vs| as in the first embodiment. In the first embodiment, when deriving formula (13) from formula (11), “xm” expressed in a per-unit system is defined as “%x”, and the approximation (%x)² << 1 is used. This approximation has essentially the same meaning as an approximation of δ ≈ 0. Therefore, the ratio between the instantaneous current command value is* and the active current command value Ip is expressed by the following formula. [Formula 16] |is*|=Ip / cos(δ+ϕ)≅Ip / cos ϕ

[0090] Formula (16) is then replaced by formula (15) and the following formula is obtained. [Formula 17] Iq3=Ip tan ϕ+kI2p / cos2ϕ

[0091] The desired reactive current is defined as a second reactive current command value Iq2. Additionally, the alternating current i s controlled in such a way that the alternating current i s This is consistent with the instantaneous current command value is*. Therefore, it is only required that the instantaneous current command value is* has a component orthogonal to the converted secondary operating voltage vs, which component is consistent with the second reactive current command value Iq2.

[0092] Additionally, the instantaneous current command value is* has a component that is in phase with the converted secondary operating voltage vs, which component corresponds to the magnitude of the actual active current. With the approximation δ ≈ 0, the in-phase component that is in phase with the converted secondary operating voltage vs can be assumed to be equal to the active current command value Ip. In this case, tan φ = Iq² / Ip and 1 / cos²φ = 1 + (Iq² / Ip)² apply. Therefore, formula (17) can be deformed as in the following formula. [Formula 18] Iq3=Iq2+kI2p+kI2q2

[0093] The second term on the right-hand side of formula (18) is equal to the first reactive current command value Iq1, which is explained in the first embodiment. Furthermore, if the third term on the right-hand side of formula (18) is defined as a second reactive current command correction value Iq2', formula (18) can be expressed by the following formula. [Formula 19] Iq3=Iq1+Iq2+Iq2'

[0094] Therefore, a voltage command calculation unit calculates an AC voltage based on the reactive current command value Iq3, which is calculated by formula (19), thereby achieving a desired reactive current, even in the presence of a phase difference angle δ. A configuration of the current command value calculation unit that achieves this function is as shown in Fig. 19, for example. Fig. Figure 19 shows a block diagram illustrating an example of a configuration of the current command value calculation unit according to the second embodiment. Fig. 19 are components that are the same as or equivalent to those in Fig. 14 are designated by the same reference symbols.

[0095] A current command value calculation unit 32C, which is in Fig. Figure 19 further shows a second reactive current command value calculation unit 326 and a second correction calculation unit 327 in the configuration of the Fig. 14 up. In Fig. The second reactive current command value calculation unit 326 calculates the second reactive current command value Iq2 for the purpose of, for example, stabilizing the operation of the converter under light load, or stabilizing the operating voltage in conjunction with an AC power supply. The second correction calculation unit 327 calculates a second reactive current command correction value Iq2' proportional to the square of the second reactive current command value Iq2, based on the second reactive current command value Iq2 and the coefficient k, which is a proportionality coefficient. The second reactive current command value Iq2 and the second reactive current command correction value Iq2' are then added by adder 328. The result of the addition provided by adder 328 is added to the first reactive current command value Iq1 by adder 329.A result of the addition by the adder 329 is output as a reactive current command value Iq3 to the voltage command value calculation unit 34.

[0096] Note that in Fig. 19. A value obtained by adding the second reactive current command value Iq2 and the second reactive current command correction value Iq2' to the first reactive current command value Iq1 is added and output to the voltage command value calculation unit 34 by the adder 329. As an alternative to this configuration, the outputs can be individually output to the voltage command value calculation unit 34. In this case, it is unnecessary to state that a value obtained by adding the second reactive current command value Iq2 and the second reactive current command correction value Iq2' to the first reactive current command value Iq1 is added within the voltage command value calculation unit 34, thus providing the reactive current command value.

[0097] Fig. Figure 20 shows a block diagram illustrating an example of a configuration of the current command value calculation unit according to the second embodiment, which differs from the one in Fig. 19 is. In Fig. 20 are components in the same or corresponding to those in Fig. 17 are represented by the same reference symbols. A current command value calculation unit 32D, which is in Fig. Figure 20 is an example configuration in a case where the control unit 3 has sufficient computing capacity, as in the first embodiment. The configuration in Fig. 20 uses the first reactive current command correction value Iq1', expressed by formula (14), instead of the first reactive current command value Iq1 in formula (19). The configuration of Fig. 20 can further improve the accuracy in controlling the reactive current, so that the reactive current is a desired value.

[0098] Note that the degrees of freedom of the three variables—power factor, active current, and reactive current—are two, and if any two of these variables are determined, the remaining one is automatically determined. Because the active current is an operating quantity used to control the DC voltage so that the DC voltage remains constant, the remaining degree of freedom is either the reactive current or the power factor. Therefore, the second reactive current command value calculation unit can calculate the second reactive current command value, Iq2, based on a command value for a power factor or power factor angle (not shown), and calculate the active current command value, Ip.

[0099] As described above, according to the second embodiment, the current command value calculation unit of the control unit calculates the second reactive current command value and uses the coefficient k, described above, as the proportionality coefficient for calculating the second reactive current command correction value, which is proportional to the square of the second reactive current command value. Additionally, the current command value calculation unit outputs the second reactive current command value and the second reactive current command correction value, together with the first reactive current command value, as described in the first embodiment, to the voltage command value calculation unit.Additionally, the voltage command value calculation unit calculates the AC voltage command value based on the reference phase, which is calculated from the values ​​obtained from the second voltage sensor, the active current command value, the first reactive current command value, the second reactive current command value, and the second reactive current command correction value. As a result, in addition to the effects of the first embodiment, a desired reactive current can be achieved even in the presence of a phase difference angle, which makes it possible for the control unit to control the power factor or the amount of reactive power. Third embodiment

[0100] In a third embodiment, a case is described where the number of power converter devices is greater than one. Note that because the power converter devices and the secondary windings of the voltage transformer are connected to each other in a one-to-one ratio as described above, the number of secondary windings of the voltage transformer is, for example, two when the number of power converter devices is two.

[0101] Fig. Figure 21 shows a block diagram illustrating an example of a configuration of a main part of a power converter system according to the third embodiment. As an example of a case where the number of power converter devices is greater than one, the Fig. Figure 21 represents a configuration in which two power converter devices 10a and 10b are each connected to a secondary winding 1b of a voltage transformer 1A via a switch 12. Note that the role of the switch 12 is described later.

[0102] For an electric vehicle, as in Fig. As described in Figure 1, the load 120 is connected to the DC side of the converter 2a via the inverter 120a. The inverter 120a drives the motor 120b to apply a driving force to the electric vehicle. Additionally, if the driving force required for the electric vehicle is distributed across multiple inverters 120a, or if the power capacity per inverter 120a is large, multiple power converter devices 10a and 10b are each connected to a secondary winding 1b of the voltage transformer 1A, as shown in Figure 1. Fig. 21 connected. A device used for one appliance can also be used for another appliance if these appliances have the same power capacity. For this reason, the power converter devices are identical in rated power. Additionally, the configuration can be as described in the Fig. Figure 21 shows that the power is supplied to a plurality of power converter devices 10a and 10b via a single voltage transformer 1A, providing a smaller volume of the entire voltage transformer than a configuration having power converter devices provided in a one-to-one ratio for voltage transformer.

[0103] Fig. Figure 22 shows a diagram representing an equivalent circuit that expresses the voltage transformer used in Fig. Figure 21 shows the process using an ideal voltage transformer and coupled inductors. Fig. 22 is the 1A voltage transformer, which is in Fig. 21 is represented by an ideal voltage transformer 72 and coupled inductors 76.

[0104] In Fig. 22 represents “v1” a primary voltage, “v2a” a secondary voltage of a first group, “v2b” a secondary voltage of a second group, “v3” a tertiary voltage, “i1” a primary current, “i2a” a secondary current of a first group, “i2b” a secondary current of a second group, and “i3” a tertiary current. The other symbols represent the same as shown here. Fig. 8.

[0105] Note that the equivalent circuit in Fig. 22 circuit equations of the following formulas are satisfied. [Formula 20] il=n2i2a+n2i2b+n3i3 [Formula 21] (n2n2n3)vl−(v2av2b v3)=j(xaaxabxa3xbaxbbxb3x3ax3bx33)×(i2ai2b i3)

[0106] For the circuit equations of the equivalent circuit in Fig. 22 is the order of the reactance matrix, which increases by one; three, because the number of secondary windings changes compared to the circuit equations of the equivalent circuit in Fig. 8 increased. The third line of formula (21) is developed, and the following formula is therefore obtained. [Formula 22] v3=n3vl−j(x3ai2a+x3bi2b+x33i3)

[0107] As described above in the basic configuration, which is in Fig. 5 or Fig. As shown in Figure 7, the active current and the reactive current are each controlled based on the reference phase θ. As expressed in the second term on the right-hand side of formula (22), the tertiary voltage v3 obtained by the voltage sensor 6 can have a phase difference from that of the primary voltage v1. This results in a problem: the power factor or reactive power quantity of the AC power on the primary side of the voltage transformer 1A is not as instructed by the control unit 3. Therefore, a technique of the third embodiment is described below, which solves this problem by correcting the instantaneous current command value is*.

[0108] First, formula (22) is deformed or transformed into the following formula. [Formula 23] n2vl=(n2 / n3)v3+j(n2 / n3)(x3ai2a+x3bi2b+x33i3)

[0109] Note that in the configuration of Fig. 21. The load of the tertiary winding 1c is only the voltage sensor 6. For this reason, it can be assumed that the tertiary current i3 is zero, i3=0. Although an electric vehicle may have another load, such as an auxiliary power supply connected to the tertiary winding 1c, its power capacity is less than that of the converter of the secondary winding in most cases. Therefore, the assumption that the tertiary current i3 is ignored, i.e., that the tertiary current is zero (i3=0), is reasonable and appropriate.

[0110] Additionally, on the left side of formula (23), a value is obtained by converting the primary voltage v1 into a secondary voltage and is equal to the converted secondary operating voltage vs. Furthermore, the first term on the right side is a value obtained by converting the value obtained by the voltage sensor 6 into a secondary voltage equal to the sensor-acquired voltage v^s. Because the converters typically have the same power rating as described above, it is assumed that the secondary current i2a of the first group and the secondary current i2b of the second group in the 1A voltage transformer are equal to each other. Additionally, because each of the secondary currents of the 1A voltage transformer is equal to the AC current i s of the corresponding converter, and the alternating current i s is controlled in such a way that the alternating current i sIf the instantaneous current command value is* is, then the currents i2a, i2b, is* are equal to each other (i2a=i2b=is*). Furthermore, if a proportionality coefficient “(n2 / n3) (x3a+x3b)” in the second term on the right-hand side is defined as xm', i.e., xm'=(n2 / n3) (x3a+x3b), the following formula is obtained. [Formula 24] vs=v^s+jxm'is*

[0111] A comparison of formula (24) with formula (9) reveals that these formulas (9) and (24) differ only in that the proportionality coefficient “xm” in the second term on the right-hand side of formula (9) is replaced by “xm’” in formula (24). Therefore, assuming that xm’ / |vs| is defined as k, i.e., k = xm’ / |vs|, the reactive current command value Iq that the current command value calculation unit is to output is one of the following two. [Formula 25] Iq1=k'I2p [Formula 26] Iq1'=Iq1 / 1−(k'Ip)2

[0112] Next, the role of switch 12, which is located in [location], will be described. Fig. 21 are shown. The power converter system of an electric vehicle, which, as in Fig. As shown in Figure 21, the switch 12 can be open to stop one or more power converter devices 10 under a specific condition. Note that the specific condition is, for example, the occurrence of a malfunction in the operation of a power converter device. If a required propulsive force is lower, only a smaller number of power converter devices can be operated, which is advantageous in terms of power efficiency.

[0113] For example, it can be assumed that the power converter device 10b in the second group is stopped and by the switch 12 in the configurations of the Fig. 21 and Fig. 22 can be separated. In this case, since i2b=0, formula (23) is expressed by the following formula. [Formula 27] n2v1=(n2 / n3)v3+j(n2 / n3)(x3ai2a+x33i3)

[0114] Additionally, with i3=0, i2a=is*, xm''=(n2 / n3)x3a, and k''=xm'' / |vs| as in the first embodiment, the reactive current command value Iq that the current command value calculation unit is to output is one of the following. [Formula 28] Iq1=k"I2p [Formula 29] Iq1'=Iq1 / 1−(k"Ip)2

[0115] A comparison of formulas (28) and (29) with formulas (13) and (14) reveals that formulas (13) and (14) differ from formulas (28) and (29) only in that the coefficient k in formulas (13) and (14) is replaced by k'' in formulas (28) and (29), respectively. Therefore, when the operating state or the stopped state of a power converter device is changed, it is only necessary for the current command value calculation unit to calculate the reactive current according to formula (13) or formula (14) as in the first embodiment, changing only the coefficient k.

[0116] If the reactance matrix is ​​defined as defined by formula (21) only as an example, the coefficient k, depending on the operating state or stopped state of the power converter device 10a in a first group and the power converter device 10b in the second group, can be expressed by the following table. [Table 1] Erste Gruppe In Betrieb Gestoppt Zweite In Betrieb n2n3×x3a+x3b|vs| n2n3×x3b|vs| Gruppe Gestoppt n2n3×x3a|vs| -

[0117] Additionally, a configuration of the current command value calculation unit, which performs the function as described above, is required, as shown in Fig. 23, for example. Fig. Figure 23 shows a block diagram illustrating an example of a configuration of the current command value calculation unit according to the third embodiment. Fig. 23 are components that are the same as or corresponding to those in Fig. 14 are represented by the same reference symbols.

[0118] A current command value calculation unit 32E, which is in Fig. Figure 23 further shows a coefficient calculation unit 330 in the Fig. The configuration shown in Figure 14 is shown. Additionally, the coefficient calculation unit 330 has a first constant selector 3301 and a divider 3302.

[0119] In Fig. 23. Information about an operating state of the power converter devices is input into the first constant selector 3301. Based on the operating states of the power converter devices, the first constant selector 3301 then selects a first constant xm from a pre-held list. The divider 3302 then divides the first constant xm by a nominal value of the amplitude of the converted secondary operating voltage vs. The output of the divider 3302 is output as the coefficient k to the first reactive current command value calculation unit 324. The divider 3302 can be omitted, and instead, the results of the division of the first constant xm by the nominal value of the amplitude of the converted secondary operating voltage vs can be pre-held in the list. Subsequent operations are as described above.

[0120] Alternatively, the coefficient calculation unit 330 can be a component of the first reactive current command value calculation unit 324. As yet another alternative, the coefficient calculation unit 330 can be provided in a host control system (not shown), and the coefficient k, which is determined depending on the operating states of the power converter devices, can be entered into the current command value calculation unit.

[0121] While the technique of switching the coefficient k, which is to be used in the first reactive current command value calculation unit 324 according to the operating state or stopped state of the power converter devices, as described above, was applied to the first embodiment only as an example, a similar technique is also applicable to the second embodiment, and it need not be mentioned.

[0122] As described above, according to the third embodiment, the control unit modifies the first coefficient according to the operating or stopped state of a plurality of power transformer devices. As a result, even if the tertiary voltage obtained by the second voltage sensor has a phase difference from the primary voltage, the power factor or reactive power output of the AC power on the primary side of the voltage transformer can be controlled as directed by the control unit. Fourth embodiment

[0123] In the current command value calculation unit of the first to third embodiments, the coefficient k is determined based on the terms outside the diagonal of the reactance matrix and the amplitude of the converted secondary operating voltage vs. Of these elements, those derived from the terms outside the diagonal of the reactance matrix are desirablely variable depending on the operating states of the power converter devices, as described in the third embodiment. The amplitude of the converted secondary operating voltage vs can change depending on the states of the loads or time. In the vector diagrams of the Fig. 11, Fig. 13 and Fig. 18. The voltage drop across the reactance xm is less than the converted secondary operating voltage vs and the sensor-acquired voltage v^s. Therefore, the amplitude of the sensor-acquired voltage v^s can be treated as the amplitude of the converted secondary operating voltage vs. Calculating the amplitude of the sensor-acquired voltage v^s and, according to the value of the calculated amplitude, setting the coefficient k, which is to be used in the current command value calculation unit, makes it possible to control the power factor on the primary side of the voltage transformer 1A more accurately as instructed by the control unit 3.

[0124] A configuration of the current command value calculation unit that achieves the function as described above is in Fig. 24, for example, is shown. Fig. Figure 24 shows a block diagram illustrating an example of a configuration of the current command value calculation unit according to a fourth embodiment. Fig. 24 are components that are the same as or corresponding to those in Fig. 23 are represented by the same reference symbols.

[0125] A current command value calculation unit 32F, which is in Fig. Figure 24 further shows an amplitude calculation unit 3303 in the coefficient calculation unit 330A in the configuration of the Fig. 23. The amplitude calculation unit 3303 calculates the amplitude of the sensor-detected voltage v^s. A known technique is used for calculating the amplitude of an AC signal, and a description of this technique is therefore omitted here. A value obtained by dividing the first constant xm by an output of the amplitude calculation unit 3303 is then obtained as the coefficient k and output to the first reactive current command value calculation unit 324. More precisely, in the fourth embodiment, the value of the coefficient k is modified such that its value is inversely proportional to the output of the amplitude calculation unit 3303.

[0126] Note that, as in the Fig.23, the coefficient calculation unit 330A is a component of the first reactive current command value calculation unit 324 or may be present in a host control system that is not shown. While the technique of changing the value of the coefficient k, which is used in the current command value calculation unit, according to the amplitude of the sensor-acquired voltage v^s has been described above as applying to the third embodiment only as an example, a similar technique is also applicable to the first and second embodiments, it goes without saying.

[0127] As described above, according to the fourth embodiment, a signal proportional to the amplitude of the output of the first voltage sensor is calculated, and the value of the first coefficient is modified such that its value is inversely proportional to the calculated output. As a result, in addition to the effects of the third embodiment, the power factor on the primary side of the voltage transformer can be controlled more precisely as directed by the control unit, even in cases where the amplitude of the converted secondary operating voltage changes depending on the load conditions or time. Reference symbol list

[0128] 1, 1A Voltage transformer; 1a Primary winding; 1b Secondary winding; 1c Tertiary winding; 2a Converter; 2b Capacitor; 3 Control unit; 4 Current sensor; 5, 6 Voltage sensor; 10, 10a, 10b Power converter device; 12 Switch; 30 Phase calculation unit; 32, 32A, 32B, 32C, 32D, 32E, 32F Current command value calculation unit; 34, 35 Voltage command value calculation unit; 36 Switching command generation unit; 50 Power converter system; 60 Propulsion control; 70, 72 Ideal voltage transformer; 74, 76 Coupled inductors; 100 Electric vehicle propulsion system; 106 Power supply equipment; 108 Power line; 110 Supply system; 120 Load; 120a Inverter; 120b Motor; 300 Processor; 302 Memory; 303 Processing circuits; 304 Interface; 320 Active current command value calculation unit; 321, 346, 352, 353 Subtractor; 322 Voltage control unit; 323, 343, 344 Multiplier; 324 First reactive current command value calculation unit; 325 First correction calculation unit;326 Second reactive current command value calculation unit; 327 Second correction calculation unit; 328, 329, 345 Adder; 330, 330A Coefficient calculation unit; 336 Tangent value calculation unit; 341 Sine value calculation unit; 342 Cosine value calculation unit; 347, 354, 355 Current control unit; 351 Rotation coordinate transformation unit; 356 Stationary coordinate transformation unit; 3301 First constant selector; 3302 Divider; 3303 Amplitude calculation unit.

Claims

[1] Power converter system (50) comprising: at least one power converter device (10) with a converter (2a) for converting alternating current power into direct current power, a first voltage sensor (5) for obtaining a direct current voltage generated on a direct current side of the converter, and a control unit (3) for controlling an operating state of the converter; and a voltage transformer (1) with a primary winding (1a) connected to an alternating current power supply, at least one secondary winding (1b), and a tertiary winding (1c) connected to a second voltage sensor (6), wherein the at least one secondary winding is connected to the at least one power converter device in a one-to-one ratio, wherein the control unit features: a phase calculation unit (30) for calculating a reference phase from a value obtained by the second voltage sensor; an active current command value calculation unit (321, 322) for calculating an active current command value on the basis of a deviation of a DC voltage command value from the DC voltage obtained by the first voltage sensor; a first reactive current command value calculation unit (324) for receiving the active current command value and a first coefficient as a proportionality coefficient, wherein the first coefficient is determined by coupled inductances of the voltage transformer and a received voltage of the voltage transformer, and for calculating a first reactive current command value proportional to a square of the active current command value, by using the first coefficient; and a voltage command value calculation unit (34; 35) for calculating an AC voltage command value based on the reference phase, the active current command value and the first reactive current command value. [2] Power converter system according to claim 1, wherein the control unit (3) comprises: a first correction calculation unit (325) for calculating a first reactive current command correction value Iq1' by using a formula (1) below based on the active current command value Ip, the first reactive current command value Iq1 and the first coefficient k, and The control unit outputs the first reactive current command correction value as the first reactive current command value to the voltage command value calculation unit. [Formula 1] Iq1'=Iq1 / 1−(kIp)2 [3] Power converter system according to claim 1 or 2, wherein the control unit (3) comprises: a second reactive power instruction calculation unit (326) for calculating a second reactive power instruction value; and a second correction value calculation unit (327) for calculating a second reactive current command correction value proportional to a square of the second reactive current command value, by using the first coefficient as a proportionality coefficient, and wherein the control unit adds the second reactive current command value and the second reactive current command correction value to the first reactive current command value, and outputs a result value to the voltage command value calculation unit. [4] Power converter system according to claim 3, wherein the second reactive power command calculation unit (326) calculates the second reactive power command value on the basis of a power factor angle command value and the active power command value. [5] Power converter system according to one of claims 1 to 4, wherein the at least one power converter device (10) is a plurality of power converter devices, and the at least one secondary winding (1b) is a plurality of secondary windings, and the control unit (3) changes a value of the first coefficient according to operating states or stop states of the majority of power converter devices. [6] Power converter system according to any one of claims 1 to 5, wherein the control unit has an amplitude calculation unit (3303) for calculating a signal proportional to an amplitude of an output of the second voltage sensor, and The control unit changes the value of the first coefficient in such a way that the value of the first coefficient is inversely proportional to an output of the amplitude calculation unit.

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