Power conversion system

Abstract

This power conversion system provides the ability to supply power according to output requirements without requiring software changes, even when repurposing existing power conversion equipment. [Solution] The power conversion system 1 comprises a power conversion device 3 that converts power from a power source into DC power for a stationary load 2, and a control device 4 therefor. The power conversion device 3 has a first power conversion unit 3A connected to a grid power source 11, and a second power conversion unit 3B connected to a power supply line 5 to the load 2. The control device 4 has a first control unit 41 that controls the operation of the first power conversion unit 3A based on a pseudo-torque command signal based on an output command to the load 2 and a phase angle signal based on a power detection signal from the grid power source 11, and a second control unit 42 that controls the operation of the second power conversion unit 3B.

Description

Technical Field

[0001] The present invention relates to a power conversion system.

Background Art

[0002] In a power supply system or battery system for supplying power to stationary power consumption equipment, it is desired to supply power that meets system requirements with good controllability. For example, Patent Document 1 discloses that in a power supply system in which battery units each including a battery and a converter are connected in parallel, a problem that the load of a specific unit increases due to power deviation caused by sensor errors or control response delays is addressed. To suppress this problem, a control device that performs voltage control of the converter for each unit is provided.

[0003] Patent Document 1 also proposes a system that repurposes battery packs and control units in order to promote recycling and reuse of recovered products from vehicles. For example, the converter of each battery unit is a repurposed power conversion device configured as a three-phase inverter, and a chopper circuit including each phase of the three-phase inverter is configured as a converter corresponding to one battery pack, and performs control based on an output voltage command.

Prior Art Literature

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] The power supply system described in Patent Document 1 includes a plurality of battery units, each of which is a converter using a phase of a three-phase inverter and connected to a battery pack. Each battery unit's converter is individually controlled by feeding back the unit's output voltage. In this case, for example, the control method set for a rotating machine cannot be used, and it was necessary to change the software for switching control of each phase.

[0006] This invention has been made in view of the above problems, and provides a power conversion system that can supply power according to output requirements without changing the software, even when existing power conversion devices are repurposed. [Means for solving the problem]

[0007] One aspect of the present invention is, A power conversion system (1) that supplies DC power to a stationary load (2), It comprises a power conversion device (3) that converts power from a power source into DC power, and a control device (4) that controls the power conversion device. The aforementioned power converter is A first power conversion unit (3A) that converts AC power from the grid power supply (11) to DC power, A second power conversion unit (3B) converts DC power into a different type of DC power and supplies it to the power supply line (5) to the load, It includes a DC link capacitor (12) connected between the first power conversion unit and the second power conversion unit, The control device is A first control unit (41) controls the operation of the first power conversion unit by taking a pseudo-torque command signal based on the output command signal to the load and a phase angle signal based on the power detection signal from the grid power supply as inputs, The power conversion system includes a second control unit (42) that controls the operation of the second power conversion unit. [Effects of the Invention]

[0008] In the power conversion system with the above configuration, the power conversion device converts grid power into DC power and supplies it to the load by controlling the operation of the first power conversion unit and the second power conversion unit, respectively, by the first control unit and the second control unit of the control device. The first control unit of the control device can operate the first power conversion unit by using a pseudo-torque command signal obtained by converting the output command signal to the load into torque representing rotational force in rotational motion, and a phase angle signal obtained by converting the power detection signal from the grid power supply into the phase of a signal wave. This makes it possible to repurpose power conversion devices and control devices that perform control based on torque command signals, for example.

[0009] As described above, according to the above embodiment, even when existing power conversion equipment is repurposed, a power conversion system can be provided that can supply power according to output requirements without requiring any software changes. The reference numerals in parentheses in the claims and the means for solving the problem indicate the correspondence with the specific means described in the embodiments later, and do not limit the technical scope of the present invention. [Brief explanation of the drawing]

[0010] [Figure 1] A block diagram showing the schematic configuration of the power conversion system in Embodiment 1. [Figure 2] A block diagram showing the configuration of the control device for the power conversion system in Embodiment 1. [Figure 3] A circuit diagram showing the schematic configuration of the power conversion system in Embodiment 2. [Figure 4] A block diagram showing an example of the configuration of the first control unit of the control device in Embodiment 2. [Figure 5] A block diagram showing an example of the configuration of the second control unit of the control device in Embodiment 2. [Figure 6] A circuit diagram showing the schematic configuration of the power conversion system in Embodiment 3. [Modes for carrying out the invention]

[0011] (Embodiment 1) Hereinafter, Embodiment 1 related to a power conversion system will be described with reference to the drawings. As shown in Fig. 1, the power conversion system 1 of the present embodiment supplies DC power to a stationary load 2. The power conversion system 1 includes a power conversion device 3 that converts source power into DC power, and a control device 4 that controls the power conversion device.

[0012] The power conversion device 3 includes a first power conversion unit 3A and a second power conversion unit 3B. The first power conversion unit 3A is connected to a system power supply 11 serving as a power source, and converts AC power into DC power. The second power conversion unit 3B converts DC power into different DC power, and supplies the converted DC power to a power supply line 5 for the load 2. The power conversion device 3 further includes a DC link capacitor 12. The DC link capacitor 12 is connected between the first power conversion unit 3A and the second power conversion unit 3B.

[0013] The power conversion device 3 is connected to the system power supply 11 via a supply wiring 13. The system power supply 11 is, for example, a three-phase AC power supply, and three-phase AC power serving as source power is supplied to the power conversion device 3 via the supply wiring 13. An inductor 14 is provided on the supply wiring 13. This suppresses noise such as switching noise in the power conversion device 3 from entering the system power supply 11.

[0014] The power conversion device 3 is connected to the load 2 via the power supply line 5. The power supply line 5 includes a positive-side wiring 5a connected to a positive electrode of the load 2, and a negative-side wiring 5b connected to a negative electrode of the load 2. The load 2 is, for example, a stationary power consumption facility, a power storage device, or the like. Examples of the power consumption facility include an electrolysis device that electrolyzes a raw material such as water vapor to generate hydrogen.

[0015] The control device 4 includes a first control unit 41, a second control unit 42, and a control command unit 43. The first control unit 41 generates a control signal for controlling the operation of the first power conversion unit 3A, and the second control unit 42 generates a control signal for controlling the operation of the second power conversion unit 3B. The configuration and operation of the power conversion device 3 including the first power conversion unit 3A and the second power conversion unit 3B will be described in Embodiment 2 described later.

[0016] As shown in FIG. 2, the first control unit 41 of the control device 4 is configured to control the operation of the first power conversion unit 3A by receiving, as inputs, a pseudo torque command signal based on an output command signal to the load 2 and a phase angle signal based on a power detection signal from the system power supply 11. Further, the control command unit 43 includes a pseudo signal generation unit 431. The pseudo signal generation unit 431 is configured to generate a pseudo torque command signal based on an output command to the load 2, calculate a phase angle signal based on a detection signal of power supplied from the system power supply 11, and further generate a pseudo rotation angle signal. The control command unit 43 may further include a DC link voltage command unit 432 that generates a DC link voltage command signal.

[0017] The pseudo torque command signal is a signal for inputting a power output command signal to the load 2 as a signal processable by the first control unit 41, and corresponds to a signal for commanding rotational torque in rotational motion, for example, a torque command representing the rotational force required for a rotating machine. For example, the pseudo signal generation unit 431 can perform arithmetic processing on a DC power output command required for the load 2 (e.g., a current command or a voltage command) using a detection signal of DC power supplied to the load 2, thereby converting the command into a rotational torque equivalent signal, which is a signal corresponding to rotational torque in rotational motion, and output the converted signal as a pseudo torque signal.

[0018] Furthermore, the pseudo-rotation angle signal corresponds to the rotational position signal in rotational motion, for example, the rotation angle in a rotating machine. When a rotation angle signal is required as an input signal to the first control unit 41, the phase angle signal can be further converted into a rotation angle equivalent signal, which is a signal corresponding to the rotation angle in rotational motion, and output. The pseudo-signal generation unit 431 can, for example, perform calculation processing using the phase signal of the DC power supplied from the grid power supply 11 (for example, current phase or voltage phase) and the phase conversion value of the power factor command, convert it into a signal corresponding to the rotation angle signal, and output it as a pseudo-rotation angle signal.

[0019] Next, the effects of the power conversion system 1 having this configuration will be explained. In the control device 4 that controls the power conversion device 3, the control command unit 43 uses an output command to the load 2 to perform a preset process and generate a pseudo-torque command signal. The output command signal is, for example, an output current command signal. The control command unit 43 also uses a detection signal of power supplied from the grid power supply 11 to perform a preset process and generate a phase angle signal (or pseudo-rotation angle signal). The detection signal of power supplied is, for example, a detection signal of the current phase or voltage phase of the grid power.

[0020] The first control unit 41 receives these pseudo-torque command signals and phase angle signals (or pseudo-rotation angle signals) and generates and outputs a control signal to control the operation of the first power conversion unit 3A. This drives the first power conversion unit 3A, converting the AC power of the grid power supply 11 into DC power and charging the DC link capacitor 12. This DC power is further converted by the second control unit 42 to the second power conversion unit 3B, which drives the second power conversion unit 3B, and supplied to the load 2 from the power supply line 5. Details of the control of the control device 4, including the first control unit 41 and the second control unit 42, will be explained in Embodiment 2 below.

[0021] The first power conversion unit 3A and the second power conversion unit B of the power conversion device 3 in this embodiment of the power conversion system 1 have a configuration similar to that of the inverter unit and converter unit used in, for example, the power conversion device of a power control unit (PCU) for electric vehicles. Furthermore, the first control unit 41 and the second control unit 42 of the control device 4 also have a configuration similar to those used to control the inverter or converter in the control device of a PCU. Therefore, since components manufactured for in-vehicle PCUs can be used as is, they can be adapted to a wide range of applications and are suitable for reuse and recycling.

[0022] Thus, according to this embodiment, a power conversion system 1 for supplying DC power from a grid power source 11 to a stationary load 2 can be configured using existing equipment. In this case, power can be supplied according to the output demand without making any software changes within the existing equipment, so a high-performance power conversion system 1 can be realized at low cost.

[0023] (Embodiment 2) Embodiment 2 of the power conversion system will be described with reference to Figure 3. As shown in the figure, the power conversion system 1 of this embodiment is an example of a specific configuration of the power conversion device 3 and the control device 4. The other basic configurations are the same as those of Embodiment 1 and will not be described. In addition, among the reference numerals used in Embodiment 2 and later, those that are the same as those used in the previously described embodiments represent the same components, etc., as those in the previously described embodiments, unless otherwise specified.

[0024] As shown in Figure 3, the power conversion system 1 of this embodiment comprises a power conversion device 3 and its control device 4, and converts three-phase AC power from the grid power supply 11 into DC power supplied to a stationary load 2. The main parts of the power conversion device 3 and the control device 4 can be configured using, for example, a PCU for rotating machinery such as an on-board motor.

[0025] The power conversion device 3 comprises a first power conversion unit 3A, a DC link capacitor 12, and a second power conversion unit 3B, all connected in parallel between the high-potential wiring 101 and the low-potential wiring 102. The first power conversion unit 3A is configured as a three-phase inverter (three-phase full-bridge circuit) and has three legs 31u, 31v, and 31w corresponding to the three phases (i.e., U-phase, V-phase, and W-phase). The second power conversion unit 3B is configured as a converter and has one leg 32, a reactor 33, and a filter capacitor 34.

[0026] Specifically, the three legs 31u, 31v, and 31w of the first power conversion unit 3A are each formed by a series connection of an upper arm switch 311u, 311v, and 311w with a lower arm switch 312u, 312v, and 312w. These three legs 31u, 31v, and 31w are connected in parallel between the high-potential side wiring 101 and the low-potential side wiring 102. The midpoints of the three legs 31u, 31v, and 31w are connected to each of the three supply wires 13 of the grid power supply 11. The midpoints of the legs 31u, 31v, and 31w are the connection points of the series connections of the upper arm switches 311u, 311v, and 311w and the lower arm switches 312u, 312v, and 312w for each phase.

[0027] Leg 32 of the second power conversion unit 3B consists of a series connection of an upper arm switch 321a and a lower arm switch 321b. The midpoint of leg 32 is connected to output wiring 322. Output wiring 322 is connected to the positive side wiring 5a of the power supply line 5, and the negative side wiring 5b is connected to the low-potential side wiring 102 of the power conversion device 3. A reactor 33 is connected in series to the output wiring 322 of leg 32, and a filter capacitor 34 is connected between the output wiring 322 and the low-potential side wiring 102 on the load 2 side of the reactor 33.

[0028] The control device 4 uses the first control unit 41 to control the switching operation of the upper and lower arm switches of each leg 31u, 31v, and 31w of the first power conversion unit 3A to turn them on and off, and uses the second control unit 42 to control the switching operation of the upper and lower arm switches of leg 32 of the second power conversion unit 3B to turn them on and off.

[0029] In the first power conversion unit 3A, the three upper arm switches 311u, 311v, and 311w and the three lower arm switches 312u, 312v, and 312w corresponding to each phase consist of, for example, gate voltage controlled IGBTs (insulated gate bipolar transistors). Each IGBT has a freewheeling diode connected in reverse between the collector and emitter. The upper and lower arms may be composed of gate voltage controlled semiconductor switching elements other than IGBTs, for example, MOSFETs (MOS field-effect transistors) can be used. The upper arm switch 32 and lower arm switch 312 constituting the second power conversion unit 3B can have a similar configuration.

[0030] As shown in Figures 4 and 5, the control device 4 includes a first control unit 41 and a second control unit 42, and a control command unit 43 that generates and outputs control command signals to these control units. The control command unit 43 is provided with a pseudo-signal generation unit 431 that generates a control command signal to the first control unit 41, and a DC link voltage command unit 432 that generates a control command signal to the second control unit 42.

[0031] In Figure 4, the first control unit 41 generates gate command signals that command the switching operation of each leg 31u, 31v, and 31w in the first power conversion unit 3A, based on the pseudo-torque command signal input from the pseudo-signal generation unit 431 of the control command unit 43 and the pseudo-rotation angle signal from the load 2 (in this case, the pseudo-resolver signal). The pseudo-signal generation unit 431 generates a pseudo-torque command signal based on the output command to the load 2 and generates a pseudo-rotation angle signal based on the detection signal of the power supplied from the grid power supply 11.

[0032] Specifically, the first control unit 41 includes a first input unit 411 to which a pseudo-torque command signal is input, a second input unit 412 to which a pseudo-rotation angle signal is input, and an output unit 413 to which a gate command signal is output. The gate command signal is obtained by comparing the duty cycle command signal for each phase with a carrier signal using pulse width modulation (PWM) control and converting it into a square wave signal. The duty cycle is the on / off time ratio of the upper and lower arms of each leg 31u, 31v, and 31w, and is generated by the duty cycle command generation unit 414 based on the pseudo-torque command signal, the pseudo-rotation angle signal, and detection signals from each unit.

[0033] In the first input unit 411, the input pseudo-torque command signal is converted into a d-axis current command signal and a q-axis current command signal (i.e., the Id command and Iq command shown in Figure 4) by coordinate transformation using, for example, a dq rotation coordinate system, and input to the first calculation unit 415. In the second input unit 412, a pseudo-resolver signal, which is, for example, a sin / cos two-phase signal, is input as a pseudo-rotation angle signal, and after being converted back into a phase angle signal by an RD converter, it is input to the first conversion unit 416. The first conversion unit 416 receives current detection signals for each phase from the supply wiring 13 connected to the first power conversion unit 3A, and the phase angle signal and the d-axis current signal and q-axis current signal based on the phase angle signal are input to the first calculation unit 415.

[0034] The first calculation unit 415 converts the d-axis current command signal and the q-axis current command signal into dq voltage command signals (i.e., Vd command and Vq command shown in Figure 4) by PI control based on the difference between them and the detected dq current signals (i.e., Id and Iq shown in Figure 4). Furthermore, this dq voltage command signal can be converted into a three-phase voltage command signal using the re-converted phase angle signal and output to the duty cycle command generation unit 414.

[0035] The pseudo-signal generation unit 431 includes a first pseudo-signal generation unit 431a that generates a pseudo-torque command signal using an output command to the load 2, and a second pseudo-signal generation unit 433 that generates a pseudo-rotation angle signal using a phase detection signal and a power factor command of the grid power supply 11. The first pseudo-signal generation unit 431a, for example, uses the DC current command signal, which is an output command to the load 2, and the detected DC current signal to perform difference-based PI control and convert it into an inverter current command signal. Furthermore, this inverter current command signal can be output as a pseudo-torque command signal by converting it using a predetermined MAP or the like.

[0036] The second pseudo-signal generation unit 433 includes, for example, a phase detection unit 433a for detecting the current phase and voltage phase of the grid power supply 11, a phase conversion unit 433b for power factor command, a second calculation unit 433c, and a second conversion unit 433d. The second calculation unit 433c performs PI control to convert the phase difference signals of the current phase and voltage phase detected by the phase detection unit 433a into a phase angle signal so that they follow the phase command signal obtained by the phase conversion unit 433b for phase conversion of the power factor command. This phase angle signal can be converted into a resolver signal by the second conversion unit 433d, and output as a pseudo-resolver signal (sin / cos).

[0037] In this way, by generating pseudo signals that can be input to the first control unit 41 using detection signals and command signals from load 2 and grid power supply 11, a gate command signal to the first power conversion unit 3A can be generated, enabling appropriate switching control. In this case, the DC power (voltage or current) supplied to load 2 can be controlled by a pseudo torque command signal based on the requested output of load 2. Furthermore, the grid power factor can be controlled by a pseudo rotation angle signal using the detection phase and power factor command from grid power supply 11.

[0038] In Figure 5, the second control unit 42 generates a gate command signal that commands the switching operation of the leg 32 of the second power conversion unit 3B based on the DC link voltage command signal input from the DC link voltage command unit 432 of the control command unit 43. The second control unit 42 can, for example, in the calculation unit 422, calculate a duty cycle command by PI control based on the DC link voltage command signal input to the signal input unit 421 and the voltage detection signal from the DC link capacitor 12, and generate a gate command signal based on PWM control.

[0039] In this case, it is desirable that the DC link voltage be controlled so that the voltage utilization rate of the grid power supply 11 does not exceed 100%, preferably so that it is 100%. Specifically, the DC link voltage command unit 432 can calculate a DC link voltage command value by adding the calculated values ​​from the feedforward control unit 432a, which is based on the voltage detection signals of each phase supplied from the grid power supply 11, and the feedback control unit 432b, which is based on the voltage detection signal from the DC link capacitor 12, and output it to the second control unit 42.

[0040] The feedforward control unit 432a can be set so that the voltage utilization rate, expressed by the following formula (1), becomes 100%. Equation (1): Voltage utilization rate = [Positive peak value of each phase voltage - Negative peak value / DC link voltage] × 100 (%) Specifically, the maximum amplitude of each phase voltage is calculated from the detection signal (absolute value), and twice that value is used as the DC link voltage command value (feedforward term), resulting in a voltage utilization rate of 100%.

[0041] Preferably, the DC link voltage command signal is set using the feedback control unit 432b, taking into account the effect of DC link voltage oscillations on the voltage utilization rate. The actual DC link voltage oscillates due to the influence of carrier components, etc., and when it oscillates to the negative side, the voltage utilization rate may exceed 100%. Therefore, by detecting the lower limit voltage of the DC link voltage and calculating and adding the feedback term using PI control based on the difference with the feedforward term, the lower limit voltage can be controlled to be equivalent to that when using the feedforward term.

[0042] In general vehicle PCUs, control may be performed with a voltage utilization rate exceeding 100%, but exceeding 100% causes distortion in each phase current due to harmonic components, making it difficult to guarantee the distortion rate specified by the grid power supply 11. On the other hand, increasing the DC link voltage to reduce the voltage utilization rate increases current ripple. Therefore, it is desirable to control the DC link voltage so that the voltage utilization rate is as close to 100% as possible while maintaining it below 100%.

[0043] Thus, with the power conversion system 1 of this embodiment, the switching operations of the first power conversion unit 3A and the second power conversion unit 3B can be efficiently controlled by the first control unit 41 and the second control unit 42. The first power conversion unit 3A and the second power conversion unit 3B, and the first control unit 41 and the second control unit 42 can be configured using existing equipment, and power can be supplied according to the output request without any software changes. Therefore, a high-performance power conversion system 1 can be realized at low cost. Furthermore, the same effects and advantages as in Embodiment 1 can be obtained.

[0044] (Embodiment 3) Embodiment 3 of the power conversion system will be described with reference to Figure 6. As shown in the figure, the configuration of the power conversion device 3 in this embodiment of the power conversion system 1 differs from that of Embodiment 1.

[0045] In this embodiment, the power converter 3 further includes a reactor 33A and a filter capacitor 34A after the second power converter 3B in Embodiment 1. The reactor 33A is connected in series with the output wiring 322 of the leg 32, on the load 2 side of the filter capacitor 34 of the second power converter 3B. The filter capacitor 34A is connected between the output wiring 322 and the low-potential wiring 102, on the load 2 side of the reactor 33A.

[0046] According to this embodiment, by providing reactor 33A and filter capacitor 34A in addition to reactor 33 and filter capacitor 34, it becomes possible to reduce DC current ripple. As a result, for example, if the power converter 3 is repurposed, the desired DC power can be stably supplied to the load 2 by adding reactor 33A and filter capacitor 34A to the downstream stage without changing its configuration. Furthermore, the same effects and advantages as in Embodiment 1 can be obtained.

[0047] The present invention is not limited to the embodiments described above, and can be applied to various embodiments without departing from its spirit. [Explanation of Symbols]

[0048] 1. Power Conversion System 11 Grid power supply 2 loads 3. Power converter 3A First Power Conversion Unit 3B Second Power Conversion Unit 4. Control device 41 First Control Unit 42 Second Control Unit 5 Power supply line

Claims

1. A power conversion system (1) that supplies DC power to a stationary load (2), It comprises a power conversion device (3) that converts power from an electrical source into DC power, and a control device (4) that controls the power conversion device. The aforementioned power converter is A first power conversion unit (3A) that converts AC power from the grid power supply (11) to DC power, A second power conversion unit (3B) converts DC power into a different type of DC power and supplies it to the power supply line (5) to the load, It includes a DC link capacitor (12) connected between the first power conversion unit and the second power conversion unit, The control device is A first control unit (41) controls the operation of the first power conversion unit by taking a pseudo-torque command signal based on the output command signal to the load and a phase angle signal based on the power detection signal from the grid power supply as inputs, A power conversion system comprising a second control unit (42) that controls the operation of the second power conversion unit.

2. The control device further includes a control command unit (43) that generates the pseudo-torque command signal and the phase angle signal and outputs them to the first control unit, The power conversion system according to claim 1, wherein the control command unit converts the power output command signal to the load into a rotational torque equivalent signal, which is a signal corresponding to the rotational torque in rotational motion, using the power detection signal from the load, and outputs it as the pseudo-torque command signal.

3. The power conversion system according to claim 2, wherein the control command unit calculates the phase angle signal based on the phase detection signal of the power supply and the phase command signal based on the power factor command in the grid power supply, converts it into a rotation angle equivalent signal which is a signal corresponding to the rotation angle in rotational motion, and outputs it as a pseudo-rotation angle signal.

4. The power conversion device further includes a DC link capacitor (12) connected between the first power conversion unit and the second power conversion unit. The power conversion system according to claim 1, wherein the second control unit controls the operation of the second power conversion unit based on a DC link voltage command signal to the DC link capacitor and a voltage detection signal from the DC link capacitor.

5. The power conversion system according to claim 4, further comprising a DC link voltage command unit (432) that generates the DC link voltage command signal based on the power supply detection signal.

6. The aforementioned power supply system is a three-phase AC power supply. The power conversion system according to any one of claims 1 to 5, wherein the first power conversion unit is configured as a three-phase full-bridge circuit.

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