Control circuit and storage battery system

Abstract

To provide a control circuit that is capable of continuously switching between effective power control and DC voltage control.SOLUTION: A control circuit 6 that controls a power conversion circuit 2 that converts between DC power and AC power, comprises: a current control unit 37 that converts a three-phase current signal resulting from detection of a three-phase input and output current on an AC side of the power conversion circuit 2 into a d-axis current signal and a q-axis current signal, and controls them to target values; a DC voltage control unit 31 that generates a target value Id* of a d-axis current; a d-axis range setting unit 34 that sets a limit range of the target value Id* by switching it between a first limit range set on the basis of the valid power target value P* and a second limit range set regardless of the valid power target value P*; and a d-axis target limit unit 33 that limits the target value Id* in the limit range set by the d-axis range setting unit 34. The DC voltage control unit 31 generates, as the target value Id*, a DC voltage compensation value for controlling a DC voltage that is input and output by the power conversion circuit 2 to the DC voltage target value Vdc*.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control circuit for controlling a power conversion circuit and a battery system including the control circuit.

Background Art

[0002] Currently, in energy management using IoT, for the spread of renewable energy and for stable power supply, the importance of a battery system that stores power in a battery (including the battery mounted on an electric vehicle) is increasing. In addition, stable and efficient operation of the battery is required. In a battery system, charging and discharging of the battery are performed using a power conversion device (so-called power conditioner) that converts DC power and AC power. When controlling the battery, the power conversion device usually controls the DC current or AC power to be constant as a constant current or constant power. In addition, the power conversion device may fully use the chargeable range of the battery for charging and discharging, or correct the state of the battery using a fully charged state where the battery is fully charged or an empty state where the battery is fully discharged. In these cases, the power conversion device needs to perform constant DC voltage control in order to stabilize the state of the battery near the terminals of 0% or 100% of the state of charge (SoC).

[0003] Patent Document 1 discloses a grid-connected inverter system that converts DC power output from a DC power source into AC power by an inverter circuit and supplies the AC power to the power grid. The control circuit of the grid-connected inverter system includes a current control unit that converts the detected three-phase output current into a d-axis current signal and a q-axis current signal perpendicular to the rotating coordinate system and controls each to a target value. Patent Document 1 also discloses an embodiment in which the control circuit includes a DC voltage control unit that controls the DC voltage and an embodiment in which the control circuit includes an active power control unit that controls the active power. By providing both the active power control unit and the DC voltage control unit and switching between them, it is possible to switch between normal active power control and DC voltage control.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent No. 6437807 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] However, since the control methods for active power control and DC voltage control are completely different, when switching the control, in some cases, it may be necessary to disconnect from the power grid once.

[0006] The present invention has been conceived under the above circumstances, and an object thereof is to provide a control circuit capable of continuously switching between active power control and DC voltage control, and a battery system including the control circuit. [Means for Solving the Problems]

[0007] The control circuit provided by the first aspect of the present invention is a control circuit that controls a power conversion circuit that converts DC power and AC power. The control circuit includes: a current control unit that converts three-phase current signals detected from three-phase input / output currents on the AC side of the power conversion circuit into a d-axis current signal and a q-axis current signal, which are two orthogonal components in a rotating coordinate system, and controls each to a target value; a d-axis current target value generation unit that generates a d-axis target value, which is a target value of the d-axis current signal; a d-axis range setting unit that switches and sets the limit range of the d-axis target value between a first limit range set based on an active power target value, which is a target value of the active power input / output by the power conversion circuit, and a second limit range set independently of the active power target value; and a d-axis target limit unit that limits the d-axis target value to the limit range set by the d-axis range setting unit. The d-axis current target value generation unit generates a DC voltage compensation value for controlling the DC voltage input / output by the power conversion circuit to a DC voltage target value as the d-axis target value.

[0008] In a preferred embodiment of the present invention, the DC voltage target setting unit for setting the DC voltage target value is further provided. When the active power target value is a positive value, the DC voltage target setting unit sets a first target value as the DC voltage target value. When the active power target value is a negative value, the DC voltage target setting unit sets a second target value as the DC voltage target value.

[0009] In a preferred embodiment of the present invention, the d-axis range setting unit calculates an upper limit value Idref based on the following formula, and the first limit range is a range equal to or less than the upper limit value Idref and equal to or greater than the lower limit value (-Idref). Idref = a·|P * | / Vrms However, |P * | is the absolute value of the active power target value, Vrms is the effective value of the line-to-line voltage on the AC side input and output by the power conversion circuit, and a is a predetermined coefficient.

[0010] In a preferred embodiment of the present invention, the d-axis range setting unit sets the first limit range to be equal to or less than the upper limit value Idref and equal to or greater than the lower limit value (-Idref) based on the upper limit value Idref input from the host device, and the d-axis current target value generation unit inputs the DC voltage target value from the host device.

[0011] The battery system provided by the second aspect of the present invention includes the battery system provided by the first aspect of the present invention, the power conversion circuit with the AC side connected to the power grid, and a battery connected to the DC side of the power conversion circuit.

Advantages of the Invention

[0012] According to the present invention, the d-axis current target value generation unit generates a DC voltage compensation value for controlling the DC voltage input and output by the power conversion circuit to the DC voltage target value as the d-axis target value. The d-axis target limitation unit limits the d-axis target value to the limitation range set by the d-axis range setting unit. When the d-axis range setting unit sets a first limitation range set based on the active power target value, the active power input and output by the power conversion circuit is suppressed to the active power target value by limiting the d-axis target value to the first limitation range. Therefore, the control circuit according to the present invention can perform active power control. On the other hand, when the d-axis range setting unit sets a second limitation range, the control circuit according to the present invention can perform DC voltage control. Further, the control circuit according to the present invention can continuously switch between active power control and DC voltage control only by switching the limitation range set by the d-axis range setting unit between the first limitation range and the second limitation range.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the accompanying drawings.

[0015] FIG. 1 is a block diagram showing the overall configuration of a battery system A1 including a control circuit according to the first embodiment. The battery system A1 includes a battery 1 and a power conversion device 9. The battery 1 is a secondary battery that can repeatedly charge and discharge, and is, for example, a lithium-ion battery. Note that the battery 1 may be other secondary batteries such as nickel-metal hydride batteries, nickel-cadmium batteries, and lead-acid batteries. Note that the battery 1 may be a capacitor such as an electric double layer capacitor instead of a secondary battery.

[0016] The power conversion device 9 is a so-called power conditioner. The input / output terminals on the DC side of the power conversion device 9 are connected to the battery 1, and the input / output terminals on the AC side are connected to the power grid B. In the present embodiment, the power conversion device 9 is connected to a three-phase power grid B. Hereinafter, the three phases are referred to as the U phase, the V phase, and the W phase. The power conversion device 9 converts AC power supplied from the power grid B or a power generation facility (not shown) into DC power to charge the battery 1, discharges the battery 1 in a predetermined case, and converts the DC power input from the battery 1 into AC power to supply it to the power grid B or a load (not shown). The power conversion device 9 includes a power conversion circuit 2, a control circuit 6, a current sensor 71, a voltage sensor 72, and a DC voltage sensor 82.

[0017] The power conversion circuit 2 is a bidirectional inverter circuit that converts DC power and AC power. The input / output terminals on the DC side of the power conversion circuit 2 are connected to the storage battery 1, and the input / output terminals on the AC side are connected to the power grid B. In practice, between the power conversion circuit 2 and the power grid B, there are connected a filter circuit for removing high-frequency components by switching and a transformer arranged for electrically insulating the power conversion circuit 2 from the power grid B, etc., but the description and explanation are omitted. The power conversion circuit 2 charges and discharges the connected storage battery 1 according to the PWM signal input from the control circuit 6. The power conversion circuit 2 charges the connected storage battery 1 by converting the AC power input from the AC side into DC power and outputting it to the DC side. Also, the power conversion circuit 2 discharges the connected storage battery 1 by converting the DC power stored in the connected storage battery 1 into AC power and outputting it to the AC side. Note that the specific internal configuration of the power conversion circuit 2 is not limited. As an example of the power conversion circuit 2, there is a three-phase full-bridge type inverter including three sets of six switching elements, etc.

[0018] The current sensor 71 detects the instantaneous values of the three-phase input / output currents on the AC side of the power conversion circuit 2 respectively. The current sensor 71 digitally converts the detected instantaneous values and outputs them to the control circuit 6 as current signals i u ,i v ,i w (The three current signals may be collectively referred to as the "current signal i"). The voltage sensor 72 detects the instantaneous values of the three-phase input / output voltages on the AC side of the power conversion circuit 2 respectively. The voltage sensor 72 digitally converts the detected instantaneous values and outputs them to the control circuit 6 as voltage signals v u ,v v ,v w (The three voltage signals may be collectively referred to as the "voltage signal v"). Also, the voltage sensor 72 calculates the effective value Vrms of the line voltage from the detected instantaneous values and outputs it to the control circuit 6.

[0019] The DC voltage sensor 82 detects the instantaneous value of the input / output voltage on the DC side of the power conversion circuit 2 (i.e., the charge / discharge voltage of the storage battery 1). The DC voltage sensor 82 digitally converts the detected instantaneous value and outputs it to the control circuit 6 as a DC voltage signal Vdc.

[0020] The control circuit 6 controls the power conversion circuit 2 and is realized by, for example, a microcomputer or the like. The control circuit 6 generates a PWM signal based on the current signal i input from the current sensor 71, the voltage signal v input from the voltage sensor 72, the effective value Vrms of the line voltage, and the DC voltage signal Vdc input from the DC voltage sensor 82. Then, the control circuit 6 outputs the generated PWM signal to the power conversion circuit 2, causing the power conversion circuit 2 to perform a power conversion operation and charging / discharging the storage battery 1 connected to the power conversion circuit 2. The control circuit 6 includes a control unit 3, a power target setting unit 4, and a power calculation unit 5.

[0021] The power calculation unit 5 calculates the active power and reactive power of the AC power input and output by the power conversion circuit 2. The power calculation unit 5 calculates the active power P and the reactive power Q based on the current signal i input from the current sensor 71 and the voltage signal v input from the voltage sensor 72, and outputs them to the control unit 3. The power calculation unit 5 extracts only the signals of the positive-phase components from the current signal i and the voltage signal v, and then calculates the active power P and the reactive power Q. Generally, the power system B includes, in addition to the positive-phase component AC signal of the fundamental wave, an inverted-phase component AC signal and a harmonic component AC signal. Due to these components other than the positive-phase components, it is difficult to accurately measure the active power and reactive power of the AC signal. Therefore, the power calculation unit 5 removes components such as the inverted-phase components and harmonic components from the current signal i and the voltage signal v, extracts only the signals of the positive-phase components, and then calculates the active power P and the reactive power Q. Note that the description of the specific configuration of the power calculation unit 5 is omitted.

[0022] The power target setting unit 4 is a functional configuration for setting target values of the active power and reactive power of the alternating current input and output by the power conversion circuit 2. The power target setting unit 4 sets the active power target value P * which is the target value of the active power input and output by the power conversion circuit 2, and outputs it to the control unit 3. Also, the power target setting unit 4 sets the reactive power target value Q * which is the target value of the reactive power input and output by the power conversion circuit 2, and outputs it to the control unit 3. The power target setting unit 4 sets the active power target value P * and the reactive power target value Q * received from an upper device (not shown). Note that the active power target value P * and the reactive power target value Q * may be set based on the operation of an operation unit (not shown) by the operator. Also, the reactive power target value Q * may be set to a fixed value (for example, "0"). When discharging the storage battery 1, a positive value is set as the active power target value P * . On the other hand, when charging the storage battery 1, a negative value is set as the active power target value P * .

[0023] The control unit 3 controls the power conversion circuit 2, and based on the current signal i input from the current sensor 71, the effective value Vrms of the line voltage input from the voltage sensor 72, the active power P and reactive power Q input from the power calculation unit 5, the DC voltage signal Vdc input from the DC voltage sensor 82, and the active power target value P * and the reactive power target value Q * input from the power target setting unit 4, generates a PWM signal and outputs it to the power conversion circuit 2.

[0024] Figure 2(a) is a block diagram showing the internal configuration of the control unit 3. As a functional configuration, the control unit 3 includes a DC voltage target setting unit 30, a DC voltage control unit 31, a reactive power control unit 32, a d-axis target limiting unit 33, a d-axis range setting unit 34, a q-axis target limiting unit 35, a q-axis range setting unit 36, a current control unit 37, and a PWM signal generation unit 38.

[0025] The DC voltage target setting unit 30 is a functional configuration for setting the target value of the DC voltage input and output by the power conversion circuit 2. The DC voltage target setting unit 30 is based on the active power target value P input from the power target setting unit 4 * to set the DC voltage target value Vdc, which is the target value of the DC voltage input and output by the power conversion circuit 2 * . The DC voltage target setting unit 30 sets the first target value Vdc_d * as the DC voltage target value Vdc for discharging the storage battery 1 when the active power target value P * is a positive value (P * ≥0). On the other hand, when the active power target value P * is a negative value (P * <0), the DC voltage target setting unit 30 sets the second target value Vdc_c * * as the DC voltage target value Vdc for charging the storage battery 1. * (>Vdc_d (>Vdc_d * ). The DC voltage target setting unit 30 outputs the set DC voltage target value Vdc * to the DC voltage control unit 31.

[0026] The DC voltage control unit 31 is a functional configuration for controlling the input and output voltage on the DC side of the power conversion circuit 2. The DC voltage control unit 31 calculates the deviation ΔVdc (=Vdc * -Vdc) between the DC voltage signal Vdc input from the DC voltage sensor 82 and the DC voltage target value Vdc input from the DC voltage target setting unit 30, and outputs a DC voltage compensation value for making the deviation zero as the target value Id * of the d-axis current. In this embodiment, the DC voltage control unit 31 performs PI control (proportional integral control). Note that control other than PI control (for example, PID control, etc.) may be performed. *

[0027] The reactive power control unit 32 is a functional configuration for controlling the reactive power input and output by the power conversion circuit 2. The reactive power control unit 32 calculates the deviation ΔQ (=Q * -Q *-Q) is calculated, and a reactive power compensation value for making the deviation zero is set as the target value Iq of the q-axis current * and output. The reactive power control unit 32 performs PI control in this embodiment. Note that control other than PI control (for example, PID control, etc.) may be performed.

[0028] As described above, the DC voltage control unit 31 and the reactive power control unit 32 perform PI control. In control including an integration operation, when a limit is provided for the output compensation value, a problem called so-called windup occurs. Therefore, it is necessary to take measures against this windup. Since a conventionally known method can be used for measures against windup, detailed description thereof is omitted.

[0029] The d-axis target limiting unit 33 is a functional configuration for limiting the target value Id output from the DC voltage control unit 31 * to the range set by the d-axis range setting unit 34. The d-axis target limiting unit 33 outputs the target value Id * limited to the set range to the current control unit 37.

[0030] The d-axis range setting unit 34 is a functional configuration for setting the limiting range of the target value Id * in the d-axis target limiting unit 33. In this embodiment, the d-axis range setting unit 34 changes the limiting range of the target value Id * depending on whether active power control is performed or DC voltage control is performed. The execution of active power control and the execution of DC voltage control are switched based on a command from a higher-level device (not shown) or an operation of an operation unit (not shown) by an operator. The d-axis range setting unit 34 includes an upper limit value calculation unit 341, an active power / current conversion unit 342, and a switching unit 343.

[0031] The upper limit value calculation unit 341 is the target value Id when DC voltage control is performed *It is a functional configuration for calculating the upper limit value. In this embodiment, when performing DC voltage control, the active power P input and output by the power conversion circuit 2 is suppressed to be equal to or less than the upper limit value P1. The upper limit value calculation unit 341 sequentially calculates the upper limit value Idmax according to the following formula (1) based on the effective value Vrms of the line voltage input from the voltage sensor 72. The upper limit value P1 is, for example, the rated power value although not limited, and is set in advance. Also, the coefficient a is a predetermined coefficient for converting to the value of the d-axis set in the d-axis target limiting unit 33, and is calculated based on the CT ratio of the current sensor 71, the VT ratio of the voltage sensor 72, the AD ratio during digital conversion, etc., and is set in advance. The target value Id * is limited to the range where it is equal to or less than the upper limit value Idmax and equal to or greater than the lower limit value (-Idmax), so that the active power P input and output by the power conversion circuit 2 is suppressed to be equal to or less than the upper limit value P1. The upper limit value calculation unit 341 outputs the calculated upper limit value Idmax to the switching unit 343. Idmax = a·P1 / Vrms ···· (1)

[0032] Note that the upper limit value Idmax of the target value Id calculated by the upper limit value calculation unit 341 * is not limited to this. For example, if it is necessary to suppress the current input and output by the power conversion circuit 2 to be equal to or less than the upper limit value I1, the upper limit value Idmax may be calculated according to the following formula (2). The upper limit value I1 is set in advance, and the power factor K is calculated from the active power P and the reactive power Q calculated by the power calculation unit 5. Also, the coefficient b is a predetermined coefficient for converting to the value of the d-axis set in the d-axis target limiting unit 33, and is calculated in the same manner as the above coefficient a and is set in advance. Idmax = b·K·I1···· (2)

[0033] The active power / current conversion unit 342 is a functional configuration for calculating the upper limit value of the target value Id * when performing active power control. In this embodiment, when performing active power control, the active power P input and output by the power conversion circuit 2 is the active power target value P input from the power target setting unit 4 *Suppress it below the absolute value thereof. The active power / current conversion unit 342 uses the effective value Vrms of the line voltage input from the voltage sensor 72 and the active power target value P input from the power target setting unit 4 * to sequentially calculate the upper limit value Idref according to the following formula (3). Note that "|P * |" indicates the absolute value of P * . By restricting the target value Id * to be within the range of not more than the upper limit value Idref and not less than the lower limit value (-Idref), the active power P input and output by the power conversion circuit 2 is suppressed to be not more than the absolute value of the active power target value P * . The active power / current conversion unit 342 outputs the calculated upper limit value Idref to the switching unit 343. Idref = a·|P * | / Vrms ···· (3)

[0034] The switching unit 343 is a functional configuration for switching the limit range of the target value Id * set in the d-axis target limiter 33 between the case of performing DC voltage control and the case of performing active power control. When performing DC voltage control, the switching unit 343 outputs the upper limit value Idmax input from the upper limit value calculation unit 341 to the d-axis target limiter 33 as the upper limit value of the target value Id * . On the other hand, when performing active power control, the switching unit 343 outputs the upper limit value Idref input from the active power / current conversion unit 342 to the d-axis target limiter 33 as the upper limit value of the target value Id * . The d-axis target limiter 33 restricts the target value Id * to be within the range of not more than the upper limit value (Idmax or Idref) input from the switching unit 343 and not less than the lower limit value ((-Idmax) or (-Idref)).

[0035] Note that when the switching unit 343 receives the active power target value P * from the power target setting unit 4, it outputs the upper limit value Idref input from the active power / current conversion unit 342, and when the active power target value P *When it is not input, the upper limit value Idmax input from the upper limit value calculation unit 341 may be output. In this case, depending on whether the active power target value P * is input, the active power control and the DC voltage control can be automatically switched.

[0036] The q-axis target limiting unit 35 is a functional configuration for limiting the target value Iq output from the reactive power control unit 32 * within the range set by the q-axis range setting unit 36. The q-axis target limiting unit 35 outputs the target value Iq * that has been limited within the set range to the current control unit 37.

[0037] The q-axis range setting unit 36 sets the limiting range of the target value Iq * in the q-axis target limiting unit 35. In this embodiment, in order to limit the power factor of the output power of the power conversion circuit 2 to be not less than Kmin and not more than 1.00, the q-axis range setting unit 36 sets the upper limit value Iqmax and the lower limit value Iqmin as the upper limit value and the lower limit value of the target value Iq * in the q-axis target limiting unit 35. The upper limit value Iqmax is sequentially calculated by the following formula (4) based on the effective value Vrms of the line voltage input from the voltage sensor 72 and the active power P input from the power calculation unit 5. Kmin is set in advance. Also, c is a predetermined coefficient for converting to the value of the q-axis set in the q-axis target limiting unit 35, and is calculated in the same manner as the above coefficient a and is set in advance. Note that the following formula (4) is derived based on the relational expression of the active power P, the reactive power Q, and the power factor K. The lower limit value Iqmin is "0". The q-axis target limiting unit 35 limits the target value Iq * to a range not exceeding the upper limit value Iqmax and not less than the lower limit value Iqmin. Note that the range set by the q-axis range setting unit 36 is not limited to this.

Equation

[0038] The current control unit 37 is a functional configuration for controlling the three-phase input / output currents on the AC side of the power conversion circuit 2. The current control unit 37 generates a current compensation value based on the current signal i input from the current sensor 71 and outputs it to the PWM signal generation unit 38.

[0039] Fig. 2(b) is a functional block diagram for explaining the internal configuration of the current control unit 37.

[0040] The current control unit 37 includes, as a functional configuration, a three-phase / two-phase conversion unit 371, a rotating coordinate conversion unit 372, LPFs 373 and 374, PI control units 375 and 376, a stationary coordinate conversion unit 377, and a two-phase / three-phase conversion unit 378.

[0041] The three-phase / two-phase conversion unit 371 is a functional configuration that performs a so-called three-phase / two-phase conversion process (αβ conversion process). The three-phase / two-phase conversion process is a process of converting a three-phase AC signal into an equivalent two-phase AC signal, which is to decompose the three-phase AC signal into the components of the orthogonal α-axis and β-axis in a stationary orthogonal coordinate system (hereinafter referred to as the "stationary coordinate system") and add the components of each axis to convert it into an AC signal of the α-axis component and an AC signal of the β-axis component. The three-phase / two-phase conversion unit 371 converts the three-phase current signals i u , i v , i w input from the current sensor 71 into an α-axis current signal i α and a β-axis current signal i β and outputs them to the rotating coordinate conversion unit 372.

[0042] The conversion process performed by the three-phase / two-phase conversion unit 371 is represented by the determinant shown in the following equation (5).

Equation

[0043] The rotation coordinate conversion unit 372 is a functional configuration that performs so-called rotation coordinate conversion processing (dq conversion processing). The rotation coordinate conversion processing is a process of converting a two-phase signal in a stationary coordinate system into a two-phase signal in a rotation coordinate system. The rotation coordinate system is an orthogonal coordinate system having orthogonal d-axis and q-axis, and rotates in the same rotation direction at the same angular velocity as the fundamental wave of the connection point voltage. The rotation coordinate conversion unit 372 converts the α-axis current signal i α and the β-axis current signal i β input from the three-phase / two-phase conversion unit 371 into the d-axis current signal i d and the q-axis current signal i q in the rotation coordinate system based on the phase θ of the fundamental wave of the connection point voltage, and outputs them.

[0044] The conversion processing performed by the rotation coordinate conversion unit 372 is represented by the determinant shown in the following equation (6).

Equation

[0045] LPF373 and LPF374 are low-pass filters, and only pass the DC components of the d-axis current signal i d and the q-axis current signal iq, respectively. By the rotation coordinate conversion processing, the fundamental wave components of the α-axis current signal i α and the β-axis current signal i β are converted into the DC components of the d-axis current signal i d and the q-axis current signal i q , respectively. That is, LPF373 and LPF374 remove unbalanced components and harmonic components and only pass the fundamental wave components.

[0046] The PI control unit 375 performs PI control based on the deviation between the DC component of the d-axis current signal i d and the target value, and outputs the current compensation value x d . The target value Id * output from the DC voltage control unit 31 and limited within the range set by the d-axis target limiting unit 33 is used as the target value of the DC component of the d-axis current signal i d . The PI control unit 376 is based on the q-axis current signal i qThe DC component and the target value Iq * Based on the deviation from the target value Iq, PI control is performed to output the current compensation value x q The target value Iq output from the reactive power control unit 32 and limited within the range set by the q-axis target limiter 35 * is used as the target value of the DC component of the q-axis current signal i q .

[0047] The stationary coordinate conversion unit 377 is a functional configuration that converts the current compensation values x d , x q input from the PI control unit 375 and the PI control unit 376 respectively into the current compensation values x α , x β in the stationary coordinate system, and performs the conversion process opposite to that of the rotating coordinate conversion unit 372. The stationary coordinate conversion unit 377 performs so-called stationary coordinate conversion processing (inverse dq conversion processing) to convert the current compensation values x d , x q in the rotating coordinate system into the current compensation values x α , x β in the stationary coordinate system based on the phase θ

[0048] The conversion process performed by the stationary coordinate conversion unit 377 is represented by the determinant shown in the following equation (7).

Equation

[0049] The two-phase / three-phase conversion unit 378 is a functional configuration that converts the current compensation values x α , x β input from the stationary coordinate conversion unit 377 into the three-phase current compensation values x u , x v , x w . The two-phase / three-phase conversion unit 378 performs so-called two-phase / three-phase conversion processing (inverse αβ conversion processing) and performs the conversion process opposite to that of the three-phase / two-phase conversion unit 371

[0050] The conversion process performed by the two-phase / three-phase conversion unit 378 is represented by the determinant shown in the following equation (8).

Equation

[0051] The PWM signal generation unit 38 is a functional configuration that generates a PWM signal. The PWM signal generation unit 38 receives the three-phase compensation signals x u , x v , x w input from the current control unit 37, and generates a command signal for commanding the waveform of the output voltage of each phase of the power conversion circuit 2. Based on the command signal and the carrier signal, a PWM signal is generated by the triangular wave comparison method. For example, a pulse signal that becomes high level when the command signal is greater than the carrier signal and becomes low level when the command signal is less than or equal to the carrier signal is generated as the PWM signal. The generated PWM signal is output to the power conversion circuit 2. Note that the PWM signal generation unit 38 is not limited to generating a PWM signal by the triangular wave comparison method, and for example, it may generate a PWM signal by a hysteresis method.

[0052] In this embodiment, the case where the control circuit 6 is realized as a digital circuit has been described, but it may also be realized as an analog circuit. Further, the processing performed by each unit may be designed by a program, and a computer may be caused to function as the control circuit 6 by executing the program. Further, the program may be recorded on a recording medium and read by a computer.

[0053] Next, the operations and effects of the control circuit 6 and the battery system A1 according to this embodiment will be described.

[0054] According to this embodiment, the current control unit 37 converts the three-phase current signals i u , i v , i w input from the current sensor 71 into a d-axis current signal i d and a q-axis current signal i q , and controls the DC components of the d-axis current signal i d and the q-axis current signal i q to their target values respectively. The DC voltage control unit 31 controls the DC voltage input and output by the power conversion circuit 2 to a DC voltage target value Vdc *as a DC voltage compensation value for control to the target value Id of the d-axis * is generated. The d-axis target limiting unit 33 limits the target value Id * within the limit range set by the d-axis range setting unit 34. When the d-axis range setting unit 34 sets the limit range based on the upper limit value Idref calculated by the active power / current conversion unit 342, the target value Id * is limited within the limit range, so that the active power input and output by the power conversion circuit 2 is suppressed to the active power target value P * . Therefore, the control circuit 6 can perform active power control. On the other hand, when the d-axis range setting unit 34 sets the limit range based on the upper limit value Idmax calculated by the upper limit value calculation unit 341, the control circuit 6 can perform DC voltage control. Further, the control circuit 6 can continuously switch between active power control and DC voltage control only by the switching unit 343 switching the limit range set by the d-axis range setting unit 34.

[0055] Also, according to the present embodiment, when the d-axis range setting unit 34 sets the limit range based on the upper limit value Idmax calculated by the upper limit value calculation unit 341, the d-axis target limiting unit 33 limits the target value Id * within the range of not more than the upper limit value Idmax and not less than the lower limit value (-Idmax). Thereby, the control circuit 6 can suppress the active power P input and output by the power conversion circuit 2 to not more than the upper limit value P1 while performing DC voltage control.

[0056] Also, according to the present embodiment, the DC voltage target setting unit 30 sets, as the DC voltage target value Vdc * , the first target value Vdc_d * for discharging when the active power target value P * is a positive value, and sets the second target value Vdc_c * for charging when the active power target value P * is a negative value. Thereby, the control circuit 6 can automatically switch between charging and discharging according to the active power target value P * .

[0057] Further, according to the present embodiment, the active power / current conversion unit 342 of the d-axis range setting unit 34 sequentially calculates the upper limit value Idref by the above formula (3) based on the active power target value P * . As a result, when the control circuit 6 performs active power control, the control circuit 6 can suppress the active power P input and output by the power conversion circuit 2 to be equal to or less than the absolute value of the active power target value P * .

[0058] In the present embodiment, the case where the power conversion device 9 performs both the conversion from DC power to AC power and the conversion from AC power to DC power has been described, but the present invention is not limited thereto. The power conversion device 9 may perform only the conversion from DC power to AC power, or may perform only the conversion from AC power to DC power. For example, when a DC power source such as a solar cell is connected instead of the storage battery 1, the power conversion device 9 may perform only the conversion from DC power to AC power. Further, when a DC load is connected instead of the storage battery 1, the power conversion device 9 may perform only the conversion from AC power to DC power.

[0059] In the present embodiment, the case where the AC side of the power conversion device 9 is connected to the power system B has been described, but the present invention is not limited thereto. The AC side of the power conversion device 9 may be connected to an AC load such as an AC motor, for example.

[0060] FIG. 3 is a block diagram showing the internal configuration of a modified example of the control unit 3 of the control circuit 6 according to the first embodiment. In FIG. 3, the same or similar elements as those in FIG. 2(a) are denoted by the same reference numerals, and redundant descriptions are omitted. In the control unit 3 according to this modified example, the d-axis range setting unit 34 includes a switching unit 344 and an upper limit value calculation unit 345. The switching unit 344 outputs a preset upper limit value P1 to the upper limit value calculation unit 345 when performing DC voltage control. On the other hand, the switching unit 344 outputs the active power target value P * input from the power target setting unit 4 to the upper limit value calculation unit 345 when performing active power control. The upper limit value calculation unit 345 calculates the target value Id * based on the upper limit value P1 or the active power target value P *Calculate the upper limit value and output it to the d-axis target limiting unit 33. That is, when the upper limit value calculation unit 345 receives the upper limit value P1 from the switching unit 344, it outputs the upper limit value Idmax calculated based on the above formula (1). When it receives the active power target value P * from the switching unit 344, it outputs the upper limit value Idref calculated based on the above formula (3). Also in this modified example, the d-axis range setting unit 34 can change the limit range of the target value Id * between the case of performing DC voltage control and the case of performing active power control.

[0061] FIG. 4 is a block diagram for explaining the battery system A2 according to the second embodiment. FIG. 4(a) is a block diagram showing the internal configuration of the control circuit 6 of the battery system A2 and an external upper device 10. FIG. 4(b) is a block diagram showing the internal configuration of the control unit 3 of the control circuit 6. In FIG. 4, the same or similar elements as those in the battery system A1 according to the first embodiment are denoted by the same reference numerals, and redundant explanations are omitted. The battery system A1 according to this embodiment is different from the battery system A1 according to the first embodiment in that the DC voltage target value Vdc * and the upper limit value Idref are input from the external upper device 10.

[0062] The upper device 10 is an upper device that transmits commands to the battery system A2. In this embodiment, the upper device 10 has the same configuration as the DC voltage target setting unit 30 and the active power / current conversion unit 342 according to the first embodiment. Based on the active power target value P * , it sets the DC voltage target value Vdc * and calculates the upper limit value Idref. Note that the internal configuration of the upper device 10 is not limited. The upper device 10 transmits the DC voltage target value Vdc * and the upper limit value Idref to the control circuit 6 (control unit 3) of the battery system A2. Also, the upper device 10 sets the reactive power target value Q * and transmits it to the control circuit 6 (control unit 3) of the battery system A2.

[0063] The control circuit 6 according to this embodiment receives the DC voltage target value Vdc from the upper device 10* is output to the DC voltage control unit 31 of the control unit 3, and the reactive power target value Q received from the host device 10 * is output to the reactive power control unit 32 of the control unit 3. Further, the control circuit 6 outputs the upper limit value Idref received from the host device 10 to the switching unit 343 of the d-axis range setting unit 34.

[0064] According to the present embodiment, when the d-axis range setting unit 34 sets a limit range based on the upper limit value Idref received from the host device 10, the target value Id * is limited to the limit range, so that the active power input and output by the power conversion circuit 2 is suppressed to the active power target value P * . Therefore, the control circuit 6 can perform active power control. On the other hand, when the d-axis range setting unit 34 sets a limit range based on the upper limit value Idmax calculated by the upper limit value calculation unit 341, the control circuit 6 can perform DC voltage control. Further, the control circuit 6 can continuously switch between active power control and DC voltage control only by the switching unit 343 switching the limit range set by the d-axis range setting unit 34. Further, according to the present embodiment, the battery system A2 has the same configuration as the battery system A1 and exhibits the same effects as the battery system A1. Furthermore, according to the present embodiment, the host device 10 can directly command the DC voltage target value Vdc * and the upper limit value Idref to the control circuit 6.

[0065] In this embodiment, the case where the host device 10 transmits both the DC voltage target value Vdc * and the upper limit value Idref to the control circuit 6 of the battery system A2 has been described, but the present invention is not limited to this. The host device 10 may transmit either the DC voltage target value Vdc * or the upper limit value Idref and the active power target value P * , and the other may be set or calculated based on the active power target value P * received by the control unit 3.

[0066] The control circuit and the battery system according to the present invention are not limited to the above-described embodiments. The specific configuration of each part of the control circuit and the battery system according to the present invention can be freely designed in various ways.

Explanation of Signs

[0067] A1, A2: Battery systems, 1: Battery, 2: Inverter circuit, 6: Control circuit, 30: DC voltage target setting unit, 31: DC voltage control unit, 33: d-axis target limiting unit, 34: d-axis range setting unit, 37: Current control unit, B: Power system

Claims

1. A control circuit for controlling a power conversion circuit that converts DC power and AC power, a current control unit that converts three-phase current signals obtained by detecting three-phase input / output currents on the AC side of the power conversion circuit into a d-axis current signal and a q-axis current signal, which are two orthogonal components in a rotating coordinate system, and controls each to a target value; a d-axis current target value generation unit that generates a d-axis target value, which is a target value of the d-axis current signal; a d-axis range setting unit that switches and sets the limit range of the d-axis target value to a first limit range set based on an active power target value, which is a target value of the active power input / output by the power conversion circuit, and a second limit range set independently of the active power target value; a d-axis target limit unit that limits the d-axis target value to the limit range set by the d-axis range setting unit; comprising the d-axis current target value generation unit generates, as the d-axis target value, a DC voltage compensation value for controlling a DC voltage input / output by the power conversion circuit to a DC voltage target value. A control circuit.

2. further comprising a DC voltage target setting unit that sets the DC voltage target value, the DC voltage target setting unit sets a first target value as the DC voltage target value when the active power target value is a positive value, and sets a second target value as the DC voltage target value when the active power target value is a negative value. The control circuit according to claim 1.

3. the d-axis range setting unit calculates an upper limit value Idref based on the following formula, the first limit range is a range equal to or less than the upper limit value Idref and equal to or greater than a lower limit value (-Idref). The control circuit according to claim 1. Idref = a · |P ＊ | / Vrms However, |P| ＊ is the absolute value of the target active power value, Vrms is the effective value of the line-to-line voltage on the AC side input and output by the power conversion circuit, and a is a predetermined coefficient.

4. the d-axis range setting unit sets the first limit range to be equal to or less than the upper limit value Idref and equal to or greater than the lower limit value (-Idref) based on the upper limit value Idref input from a higher-level device, the d-axis current target value generation unit inputs the DC voltage target value from the higher-level device. The control circuit according to claim 1.

5. The control circuit according to any one of claims 1 to 4, the power conversion circuit with its AC side connected to a power grid, a storage battery connected to the DC side of the power conversion circuit, A storage battery system comprising.

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