JP5549904B2 - Power conversion device, power conversion device control program, and recording medium recording power conversion device control program - Google Patents

Description

  The present invention relates to a power conversion device for a storage battery that can charge and discharge a plurality of storage batteries, and in particular, in a large system with a large number of batteries, performs charge / discharge control of each battery in a simple manner and the capacity of each battery. The power conversion device that does not shorten the life of the entire system depending on the degree of deterioration and capacity variation of each battery by performing charge / discharge control so that the battery can be used to the fullest extent, and the charge / discharge control method for the power conversion device The present invention relates to a power conversion device control program and a recording medium on which the power conversion device control program is recorded.

  In recent years, from the viewpoint of stable energy supply to power consumers and global environmental conservation, direct current or alternating current power generated by natural energy power generation such as solar cells and wind power generation is converted to commercial frequency alternating current using a power converter such as a power conditioner. A distributed power supply system that converts this power into electric power and supplies this AC power to a commercial power system or an AC load is becoming popular. In such natural energy power generation, the output fluctuates with fluctuations in solar radiation and air flow, so the power in the direction from the distributed power source to the substation side (reverse power flow) also fluctuates. In the future, when the amount of renewable energy increases and the proportion of renewable energy power generation in the entire power system accounts for about several tens of percent, in order to maintain the frequency of the power system within a certain range, existing thermal power As with power generation and hydropower generation, it is necessary to control the power generation output from natural energy generation according to the load demand. This is because the frequency of the power system changes in the upward direction when the amount of power generation exceeds the load demand in the power system, and the frequency of the power system changes in the downward direction when the amount of power generation is insufficient. This is because, when the penetration rate of power generation increases, the stability of the system frequency may be impaired if the power system accepts unlimited reverse power flow of natural energy power generation as in the past.

  As described above, in order to freely control the output of the distributed power system using natural energy, the surplus power of natural energy power generation is stored, and the stored power is discharged when power generation is insufficient or stopped. Therefore, it is considered that a distributed power supply system equipped with power storage means that can be supplied to a load is indispensable. In order to store the power of natural energy generation in this way, for example, in the case of a residential solar power generation system that has already been spread, the capacity of several kWh that can store several hours of solar power generation power of about 3 kW A power storage device is considered necessary. Since such a large-capacity power storage device cannot be constituted by a single battery, generally, a large-capacity power storage device is configured by an assembled battery in which a large number of single cells are connected in series or in parallel. In such a large-capacity power storage device, it is important that a large number of single cells can be used in the entire region from the end-of-discharge state to the fully charged state according to the individual battery capacity. This is because, when a unit cell having a large capacity drop due to its lifetime exists in the assembled battery, the utilization rate of the entire assembled battery may decrease due to the unit cell.

Therefore, as a conventionally proposed technique, a technique disclosed in Patent Document 1 can be cited. According to this technology, in a power supply device including a large number of batteries, shared power is output from each battery according to its own actual capacity and necessary electric power is supplied to the motor. It is said that high-load work can be continuously performed over a long period of time without limiting the battery life.
JP 2004-147477 A (published May 20, 2004)

  However, the technique described in Patent Document 1 calculates the power to be supplied to the load and the actual capacity of each battery, and then calculates the power to be allocated to each battery based on those values. It is necessary to accurately measure the actual capacity. Therefore, it is necessary to measure the voltage and current of each battery in a short cycle and collect and store the accumulated values from all the batteries. Furthermore, it is necessary to command the allocated power value to be output from each battery to the DC / DC converter to which each battery is connected, and each DC / DC converter must control the output power from the battery according to the power command. There is. Such a power supply device has a problem that since the measurement system is complicated, the system becomes complicated and the cost may increase when the number of batteries increases. Further, since the amount of processing performed by the controller increases as the number of single cells increases, there is a problem that the number of batteries that can be connected may be limited depending on the capability of the controller.

  The present invention has been made in view of the above problems, and its object is to perform charge control of each battery in a simple manner and to make maximum use of the capacity of each battery. The power conversion device, the charge / discharge control method for the power conversion device, the power conversion device control program, and the power conversion device that do not shorten the life of the entire system depending on the degree of deterioration and capacity variation of each battery It is to provide a recording medium on which a control program is recorded.

  In order to solve the above problems, a power conversion device according to the present invention is a power conversion device that converts power from a plurality of power storage means that can be charged and discharged and supplies the power to a power source. A voltage value is measured, an average value of all the measured voltage values is calculated, the calculated average value is compared with the voltage value of each power storage unit, and charging of each power storage unit is performed based on the comparison result. Charge / discharge control means for controlling discharge, and the power converter has a charge operation mode for charging each power storage means and a discharge operation mode for discharging from each power storage means, and the charge / discharge control means comprises: In the discharge operation mode, among the power storage means, a discharge output increase control for increasing the discharge power of the power storage means whose voltage value of the power storage means is greater than the average value, and the voltage value of the power storage means In the discharge output reduction control for reducing the discharge power of the power storage means smaller than the average value, and in the charge operation mode, the charge of the power storage means is greater than the average value among the power storage means. At least one of charging output decrease control for reducing power and charging output increase control for increasing the charging power of the power storage means whose voltage value of the power storage means is smaller than the average value is performed. .

  Moreover, in order to solve the said subject, the charging / discharging control method of the power converter device which concerns on this invention WHEREIN: The said power converter device which converts the electric power by the several electrical storage means which can be charged and discharged, and supplies it to an electric power source A charge / discharge control method for controlling charging and discharging of a power storage means, a measurement step for measuring the voltage value of each power storage means, and a calculation step for calculating an average value of all voltage values measured in the measurement step; A comparison step of comparing the voltage value of each power storage unit measured in the measurement step with the average value calculated in the calculation step, and charging of each power storage unit based on the comparison result in the comparison step A charge / discharge control step for controlling discharge. In the charge / discharge control step, in the discharge operation mode in which discharge is performed from each of the power storage devices, the voltage value of the power storage device among the power storage devices is A discharge output increase control step for increasing the discharge power of the power storage means greater than a value; a discharge output decrease control step for reducing the discharge power of the power storage means whose voltage value is less than the average value; and In a charging operation mode in which each power storage means is charged, among the power storage means, a charge output reduction control step for reducing charge power of the power storage means whose voltage value of the power storage means is greater than the average value; and the power storage means And at least one of the charging output increase control steps for increasing the charging power of the power storage means smaller than the average value.

  According to said structure and method, even if it is a case where the dispersion | variation in the charging / discharging characteristic of each electrical storage means exists, it controls so that the voltage of each electrical storage means may correspond. Therefore, a state in which some of the power storage means reaches the discharge lower limit voltage or the charge upper limit voltage early and the other power storage means cannot be used up to the discharge lower limit voltage or the charge upper limit voltage does not occur. It can be used over the entire voltage range, and the storage capacity of the storage means can be utilized to the maximum even after the deterioration of the storage means progresses. In addition, since it becomes difficult to reach the discharge lower limit voltage and the charge upper limit voltage, the progress of the battery deterioration can be slowed and the life can be extended.

  Furthermore, since the increase / decrease in the charge / discharge power of the power storage means is controlled based only on the current voltage value of the power storage means, it is possible to correct the variation of each power storage means without having to measure the difference in capacity of each power storage means. . Therefore, control can be simplified and cost reduction can be achieved.

  As described above, the output control of each battery is performed by a simple method, and charge / discharge control is performed so that the capacity of each battery can be utilized to the maximum, so that the system depends on the degree of deterioration of each battery and the variation in capacity. There is an effect that it is possible to provide a power conversion device and a charge / discharge control method for the power conversion device that do not shorten the entire life.

  In the power conversion device according to the present invention, the charge / discharge control means is provided for each power storage means, and adjusts a pulse width of a drive pulse for driving the switch element, whereby a charging current to each power storage means and The first power conversion means, which is a switching converter that controls the discharge current from each power storage means to charge and discharge each power storage means, and the first output conversion control during the discharge and the first output increase control during the charge. An output increase command is given to the power conversion means, and the first power conversion means is controlled by giving an output decrease command to the first power conversion means in the discharge output decrease control and the charge output decrease control. Control means, and the power converter is connected to the DC bus, the DC bus and the power source, to the power source and from the power source. Second power conversion means for converting the power of the power storage means, wherein the first power conversion means includes a power storage means side terminal connected to the power storage means, and a DC bus side terminal connected to the DC bus. And controlling the pulse width so that the DC bus side terminal voltage coincides with a target value, and the DC bus side terminals of the first power conversion means are connected in series to the DC bus. It is preferable that they are connected.

  According to the above configuration, the first power conversion means controls the output by itself so that the DC bus side terminal voltage becomes the target value even when no command is received from the control means. Can be provided. Further, since the converter is autonomous, a system having high reliability can be provided.

  In the power conversion device according to the present invention, the first power conversion means reduces the pulse width of the switch element when the measured value of the DC bus side terminal voltage is larger than the target value in the discharge operation mode. When the measured value of the DC bus side terminal voltage is smaller than the target value, the pulse width of the switch element is increased and the measured value of the DC bus side terminal voltage is larger than the target value in the charging operation mode. Increases the pulse width of the switch element, and when the measured value of the DC bus side terminal voltage is smaller than the target value, the DC bus side terminal voltage is reduced to the target value by decreasing the pulse width of the switch element. It is preferable to control so that.

  According to the above configuration, the DC bus side terminal voltage constant control is performed by increasing / decreasing the pulse width of the drive pulse for driving the switch element based on the comparison result between the measured value of the DC bus side terminal voltage and the target value. Therefore, it is possible to provide a power converter in which the input / output voltage of the converter is stably controlled in both operation of charging and discharging by simple control.

  In the power conversion device according to the present invention, when the first power conversion means receives the output increase command from the control means, the target value of the DC bus side terminal voltage is updated to a value increased from an initial value. When the output reduction command is received from the control means, it is preferable to update the target value to a value obtained by reducing the initial value.

  According to the above configuration, the voltage balance control that eliminates the voltage variation between the power storage means can be performed only by changing the target value of the DC bus side terminal voltage based on the command from the control means. The power storage capacity of the power storage means can be utilized to the maximum without performing complicated communication with the first power conversion means.

  In the power conversion device according to the present invention, it is preferable that the power source is a commercial power system, and the second power conversion unit is a grid-connected inverter circuit.

  According to said structure, in the electric power consumer in which the said power converter device was installed, since electric power can be charged from a commercial power grid or can be supplied with respect to a commercial power grid, a power consumer has Electric power load fluctuations can be leveled by the power converter, and power received by a power consumer from a commercial power system can be systematically operated.

  The control means in the power converter can be executed on a computer by a power converter control program. Furthermore, by recording the power converter control program on a computer-readable recording medium, the processing program can be executed on an arbitrary computer.

  A power conversion device according to the present invention is a power conversion device that converts power from a plurality of power storage means that can be charged and discharged and supplies the power to a power source, measures the voltage value of each power storage means, and measures the measurement Charge / discharge control means for calculating an average value of all the voltage values, comparing the calculated average value with the voltage value of each power storage means, and controlling charging and discharging of each power storage means based on the comparison result The power conversion device has a charge operation mode for charging the power storage means and a discharge operation mode for discharging from the power storage means, and the charge / discharge control means is Among the power storage means, the output increase control during discharge for increasing the discharge power of the power storage means whose voltage value is higher than the average value, and the voltage value of the power storage means is lower than the average value. In output reduction control during discharge for reducing the discharge power of the power means, and in the charge operation mode, during charging, the voltage value of the power storage means of the power storage means is greater than the average value during charging. At least one of output decrease control and charge output increase control for increasing the charging power of the power storage means whose voltage value is lower than the average value is performed.

  Also, the charge / discharge control method for a power conversion device according to the present invention controls the charging and discharging of the power storage means of the power conversion device that converts power supplied from a plurality of power storage means capable of charging and discharging and supplies the power to a power source. A charge / discharge control method for measuring a voltage value of each power storage unit, a calculation step for calculating an average value of all voltage values measured in the measurement step, and a measurement step A comparison step for comparing the voltage value of each power storage unit with the average value calculated in the calculation step, and a charge / discharge control step for controlling charging and discharging of each power storage unit based on the comparison result in the comparison step And in the charge / discharge control step, in the discharge operation mode in which discharging is performed from each power storage unit, among the power storage units, the power storage unit has a voltage value greater than the average value. A discharge output increase control step for increasing the discharge power, a discharge output decrease control step for decreasing the discharge power of the power storage device whose voltage value is lower than the average value, and charging of each power storage device In the charging operation mode, among the power storage means, a charge-time output reduction control step for reducing the charge power of the power storage means whose voltage value is higher than the average value, and the voltage value of the power storage means is the average value. It is characterized by performing at least one of the charging output increase control steps for increasing the smaller charging power of the power storage means.

  According to said structure and method, even if it is a case where the dispersion | variation in the charging / discharging characteristic of each electrical storage means exists, it controls so that the voltage of each electrical storage means may correspond. Therefore, a state in which some of the power storage means reaches the discharge lower limit voltage or the charge upper limit voltage early and the other power storage means cannot be used up to the discharge lower limit voltage or the charge upper limit voltage does not occur. It can be used over the entire voltage range, and the storage capacity of the storage means can be utilized to the maximum even after the deterioration of the storage means progresses. In addition, since it becomes difficult to reach the discharge lower limit voltage and the charge upper limit voltage, the progress of the battery deterioration can be slowed and the life can be extended.

  Furthermore, since the increase / decrease in the charge / discharge power of the power storage means is controlled based only on the current voltage value of the power storage means, it is possible to correct the variation of each power storage means without having to measure the difference in capacity of each power storage means. . Therefore, control can be simplified and cost reduction can be achieved.

  As described above, the output control of each battery is performed by a simple method, and charge / discharge control is performed so that the capacity of each battery can be utilized to the maximum, so that the system depends on the degree of deterioration of each battery and the variation in capacity. There is an effect that it is possible to provide a power conversion device and a charge / discharge control method for the power conversion device that do not shorten the entire life.

  The embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a block diagram showing a main configuration of a storage battery power conversion device 10 according to the present embodiment. First, with reference to FIG. 1, the principal part structure of the power converter device 10 is demonstrated.

  As shown in the figure, the power conversion device 10 includes a storage battery (power storage means) 1, a first converter (first power conversion means) 2, a second converter (second power conversion means) 4, and a control unit ( Control means) 7 and is connected to a power system (power source) 5. The outline of the power converter 10 is to convert the voltage from the storage battery 1 into DC power by the first converter 2, convert it to AC power by the second converter (inverter) 4, and supply it to the power system 5. The “charge / discharge control means” in the claims of the present application corresponds to the first converter 2 and the control unit 7.

  The storage battery 1 may be any secondary battery that can take out the charged DC power by discharging. For example, a lead storage battery, a nickel-hydrogen battery, a lithium ion secondary battery, or a lithium ion capacitor can be used. Moreover, as long as desired electric power is obtained, the storage battery 1 may use a single battery or an assembled battery in which a plurality of single batteries are connected in series or in parallel. In this embodiment, in consideration of the fact that a high energy density can be obtained, a lithium ion secondary battery that operates at a voltage of about 3 to 4 V is used as a single battery.

  The first converter 2 is a bidirectional DC-DC converter capable of charging and discharging DC power to the storage battery 1 by controlling the charging current to the storage battery 1 and the discharge current from the storage battery 1. 1 converter 2 is connected. The first converter 2 boosts the voltage of the storage battery 1 to a certain DC voltage during discharge operation (discharge operation mode) in which the storage battery 1 is discharged, and during charge operation (charge operation mode) in which the storage battery 1 is charged. ) Step down the voltage to the storage battery 1 to a certain DC voltage. In the present embodiment, the voltage of the storage battery 1 is boosted to 10V, and the voltage to the storage battery 1 is decreased to 3-4V.

  The first converter 2 includes a communication unit and communicates with the control unit 7 via the communication line 8. Although wired communication is assumed in FIG. 1, wireless communication may be used as long as each first converter 2 can communicate with the control unit 7. In the present embodiment, RS485 communication using a twisted pair line as the communication line 8 is applied. Further, the first converter 2 sequentially measures the voltage Vc of the storage battery 1.

  Since the power conversion device 10 has a large number of storage batteries 1, a unit in which the power storage means 1 and the first converter 2 are connected is used as a structural unit (hereinafter referred to as a subsystem), and a plurality of subsystems are connected in series. The connected battery is referred to as an assembled battery 3. Specifically, as shown in FIG. 1, the output of the first converter 2 is connected in series, and the synthesized output of the assembled battery 3 is connected to the second converter 4. In the present embodiment, 38 first converters 2 are connected in series so that the output of the assembled battery 3 is 380V.

  The assembled battery 3 is connected to the second converter 4 via a DC bus 6. The number of assembled batteries 3 may be one, but as shown in FIG. 1, the total battery capacity can be obtained by connecting a plurality of assembled batteries 3 as necessary in parallel with a DC bus 6 and inputting them to the second converter 4. Therefore, the overall battery capacity can be set flexibly according to the number of the assembled batteries 3. In the following, for the sake of convenience, the description will be made assuming that the assembled battery 3 is one.

  The second converter 4 is a bidirectional grid-connected inverter, and its output is connected to a power system 5 that is a commercial power system (single-phase AC200V distributed to a general household). The second converter 4 converts the DC 380V voltage supplied from the assembled battery 3 into an AC 200V voltage during the discharge operation (discharge operation mode) and supplies it to the power system 5, during the charge operation (charge operation mode). The rectified and boosted AC200V voltage supplied from the power system 5 is converted to a DC380V voltage and supplied to the DC bus 6 side. The second converter 4 also communicates with the control unit 7.

  The controller 7 communicates with the first converter 2 and the second converter 4 to control their operation. Information transmitted by communication between the first converter 2 and the control unit 7 includes the voltage Vc of the storage battery 1 measured by the first converter 2, the operation command of the discharge / charge operation mode, and the first converter 2. Output increase / decrease commands are included, which will be described in detail later. The information transmitted by communication between the second converter 4 and the control unit 7 includes an operation command in the discharge / charge operation mode (hereinafter referred to as “charge / discharge command”) and the like. In order to reduce the number of communication lines, it is desirable to use serial communication, but parallel communication may be used to simplify the communication method. In this case, for example, an operation command in the discharge / charge operation mode and an output increase / decrease command of the first converter are used in a signal line H / L (high / low) state using one digital signal line for each command. Can be sent.

  Further, the control unit 7 calculates the average voltage Vav by summing up the voltages Vc from all the first converters 2 in the assembled battery 3 and dividing the result by the number of the storage batteries 1, and calculates the average voltage Vc of each storage battery 1 and the average. The magnitude relationship with the voltage Vav is compared. Based on this comparison result, an output increase / decrease command for the first converter is transmitted. Details will be described later.

  The outline of the operation of the power conversion device 10 will be described. During the charging operation, the second converter 4 rectifies and boosts the voltage of AC200V supplied from the power system 5 to convert it into a voltage of DC380V, thereby converting it to the DC bus 6 side. To supply. In the assembled battery 3, the voltage of DC 380 V supplied from the DC bus 6 is divided by the number of the first converters 2 and supplied to the first converters 2. Here, approximately 10 V obtained by dividing the DC 380 V of the DC bus 6 into the 38 first converters 2 is supplied from the terminal on the DC bus 6 side of the first converter 2. The first converter 2 steps down the voltage of about 10 V supplied by dividing the voltage to a voltage of about 3 to 4 V of the storage battery 1 and charges the storage battery 1. The reverse operation occurs during the discharge operation.

  Next, details of the first converter 2 and the second converter 4 will be described with reference to FIG. FIG. 2A is a circuit diagram illustrating a specific configuration of the first converter 2, and FIG. 2B is a circuit diagram illustrating a specific configuration of the second converter 4.

  The first converter 2 is a bidirectional chopper circuit as shown in FIG. The bidirectional chopper circuit is driven by PWM (pulse width modulation) at a frequency of about 20 kHz, for example. The terminal (power storage means side terminal) BL is connected to the negative electrode side of the storage battery 1, and the terminal (power storage means side terminal) BH is connected to the positive electrode side of the power storage means 1. The terminal (DC bus-side terminal) DL is connected to the negative side (DC negative bus) of the DC bus 6, and the terminal (DC bus-side terminal) DH is connected to the positive side (DC positive bus) of the DC bus 6. MOSFETs and IGBTs can be used for the switch elements S1 and S2 of the bidirectional chopper circuit, but in this embodiment, IGBTs are used.

  During the discharge operation, the switch element S2 is always controlled to be in an off state. For this reason, only the body diode incorporated in the switch element S2 functions. The switching element S1 is switching-controlled at a high frequency of 20 kHz. For this reason, the first converter 2 operates as a step-up chopper. The voltage Vd (DC bus side terminal voltage) generated between the terminals DH and DL is controlled by controlling the duty ratio (ratio between ON time and OFF time) of the PWM signal (drive pulse) that drives the switch element S1. can do.

  On the other hand, during the charging operation, the switch element S1 is always controlled to be in an off state. For this reason, only the body diode incorporated in the switch element S1 functions. The switching element S2 is switching-controlled at a high frequency of 20 kHz. For this reason, the first converter 2 operates as a step-down chopper. By controlling the duty ratio of the PWM signal for driving the switch element S2, the voltage generated between the terminals BH and BL can be controlled.

  The second converter 4 is a full bridge type bidirectional inverter circuit as shown in FIG. The input side of second converter 4 is connected to DC negative bus side terminal TL and DC positive bus side terminal TH, and power system side terminals G 1 and G 2 are connected to power system 5. MOSFETs and IGBTs can be used for the switch elements S3 to S6 of the second converter 4, but in this embodiment, IGBTs are used.

  During the discharge operation, the DC power supplied via the terminals TL and TH is commercial frequency (50 Hz or 60 Hz) by PWM driving the switch elements S3 to S6 at a high frequency of about 20 kHz and smoothing the waveform in the filter circuit FL1. The obtained sine wave AC is output to the power system 5.

  On the other hand, during the charging operation, the switch elements S3, S5, and S6 are always controlled to be off in the positive half cycle in which the potential of the terminal G1 is higher than the potential of the terminal G2, and the switch element S4 is PWM driven at a frequency of about 20 kHz. Is done. Thereby, the step-up chopper circuit is configured by the filter circuit FL1 and the switch elements S3, S4, and S6, and the half-cycle sinusoidal voltage supplied from the terminals G1 and G2 is boosted and converted to a DC voltage of 380V. Next, for the negative half cycle in which the potential of the terminal G2 is higher than the potential of the terminal G1, the switch elements S3, S4, and S5 are controlled to be always off, and the switch element S6 is PWM-driven at a frequency of about 20 kHz. Thereby, the step-up chopper circuit is configured by the filter circuit FL1 and the switch elements S4, S5, and S6, and the half-cycle sinusoidal voltage supplied from the terminals G1 and G2 is step-up converted into a DC voltage of 380V. With the above operation, during the charging operation, the AC power of the power system 5 is rectified and boosted and supplied as DC power from the terminals TL and TH to the DC bus 6. Further, when the second converter 4 is charged, the second converter 4 is controlled by controlling the pulse width of the PWM signal for driving the switch elements S4 and S6 so that the current input from the terminals G1 and G2 becomes a sine wave. Since harmonic currents flowing out from the power system 5 to the power system 5 side are suppressed, it is more preferable.

  Next, the discharging operation performed by the first converter 2 on the storage battery 1 will be described in detail.

  When the control unit 7 transmits a discharge command to the first converter 2, the first converter 2 enters the discharge operation mode. At the same time, the control unit 7 transmits a discharge command to the second converter 4, and the second converter 4 also enters the discharge operation mode.

  The second converter 4 controls the pulse width of the PWM signal that drives the switch elements S3 to S6 so that the voltage Vt between the terminals TH and TL matches the target value 380V. Specifically, when the second converter 4 receives the discharge command from the control unit 7 and operates in the discharge operation mode, the voltage Vt is set to the target value 380 V as a result of increasing the pulse width of the switch elements S3 to S6. If it is higher, the pulse width is further increased, and if it is lower than the target value 380V, the pulse width is decreased. If the voltage Vt is higher than the target value 380V as a result of decreasing the pulse width, the pulse width is further decreased, and if the voltage Vt is lower than the target value 380V, the pulse width is increased.

  On the other hand, in the discharge operation mode, the first converter 2 controls the pulse width of the PWM signal that drives the switch element S1 so that the voltage Vd between the terminals DH and DL coincides with the target value Vdt. Here, the target value Vdt is 10V. Specifically, when the first converter 2 receives a discharge command from the control unit 7 and operates in the discharge operation mode, the pulse width of the switch element S1 is increased, but as a result of increasing the pulse width, When Vd is lower than the target value 10V, the pulse width is further increased, and when Vd is higher than the target value 10V, the pulse width is decreased. If the voltage Vd is higher than the target value 10V as a result of decreasing the pulse width, the pulse width is further decreased, and if the voltage Vd is lower than the target value 10V, the pulse width is increased.

  Next, the details of the discharge operation of the power conversion apparatus 10 as a whole by the above control will be described. When the control unit 7 gives a discharge command of 1.5 kW to the second converter 4, the second converter 4 measures the power output from the terminals G1 and G2 by itself, and the voltage Vt Is gradually increased so that the output power of the switch element S3 to S6 becomes the target value of 1.5 kW.

  Since the first converter 2 initially enters the discharge operation mode, the power output from the terminals DH and DL is almost zero, so the voltage Vt, which is the total voltage of the voltage Vd, falls below the target value 380V. Through the control described above, the first converter 2 increases the pulse width of the switch element S1 because the voltage Vd is lower than the target value 10V. In this way, each first converter 2 increases the output power, so that the voltage Vt rises and reaches the target value 380V. When the second converter 4 further increases the pulse width of the switch elements S3 to S6 toward the target value of 1.5 kW, the output power of the second converter 4 increases. Since the output power from the terminals DH and DL does not change immediately, the voltage Vt falls below the target value 380V. By repeating these control operations, the output power of the second converter 4 finally reaches 1.5 kW, the voltage Vt stabilizes in the vicinity of the target value 380V, and the voltage Vd of the first converter 2 becomes the target It stabilizes near the value of 10V. As a result, each of the first converters 2 supplies 1.5 kW of discharge power to 38 units, so that each unit has a discharge output of about 40 W.

  Next, the charging operation performed by the first converter 2 on the storage battery 1 will be described in detail. When control unit 7 sends a charge command to first converter 2 and second converter 4, each converter enters a charge operation mode.

  The second converter 4 controls the pulse width of the PWM signal that drives the switch elements S4 and S6 so that the voltage Vt between the terminals TH and TL matches the target value 380V. Specifically, when the second converter 4 receives a charge command from the control unit 7, the pulse width of the switch elements S4 and S6 is increased. As a result, when the voltage Vt is lower than the target value 380V, The pulse width is further increased. When the pulse width is higher than the target value 380V, the pulse width is decreased. As a result of reducing the pulse width of the switch elements S4 and S6, the pulse width is further reduced when the voltage Vt is higher than the target value 380V, and the pulse width is increased when the voltage Vt is lower than the target value 380V.

  In the charging operation mode, the first converter 2 controls the pulse width of the PWM signal that drives the switch element S2 so that the voltage Vd between the terminals DH and DL coincides with the target value 10V. Specifically, when the first converter 2 receives a charge command from the control unit 7, the voltage Vd is lower than the target value 10V as a result of increasing the pulse width of the switch element S 2 but increasing the pulse width. In this case, the pulse width is decreased, and when the target value is higher than 10 V, the pulse width is further increased. Further, as a result of reducing the pulse width of the switching element S2, the pulse width is increased when the voltage Vd is higher than the target value 10V, and is further decreased when the voltage Vd is lower than the target value 10V.

  Next, the details of the charging operation of the power conversion apparatus 10 as a whole by the above control will be described.

  When the control unit 7 gives a charge command of 1.5 kW to the second converter 4, the second converter 4 measures the power input from the terminals G1 and G2 by itself and sets the voltage Vt to 380V. The pulse widths of the switch elements S4 and S6 are gradually increased so that the input power thereof becomes the target value of 1.5 kW.

  In the first converter 2, since the power input from the terminals DH and DL is substantially zero at the beginning of the charging operation mode, the voltage Vt, which is the total voltage of the voltage Vd, rises from the target value 380V. By the control described above, the first converter 2 increases the pulse width of the switch element S2 because the voltage Vd is higher than the target value 10V. In this way, each first converter 2 increases the output, whereby the voltage Vt decreases and reaches the target value 380V. When the second converter 4 further increases the pulse width of the switch elements S4 and S6 toward the target value of 1.5 kW, the input power of the second converter 4 increases. Since the input power from the terminals DH and DL does not change immediately, the voltage Vt rises from the target value 380V. By repeating these control operations, the input power of the second converter 4 finally reaches 1.5 kW, the voltage Vt stabilizes near the target value 380 V, and the voltage Vd of the first converter 2 becomes the target It stabilizes near the value of 10V. As a result, each of the first converters 2 supplies 1.5 kW of charging power by 38 units, so that the charging output of about 40 W per unit is obtained.

  As described above, the first converter 2 increases or decreases the pulse width of the PWM signal that drives the switch elements S1 and S2 based on the comparison result between the measured value of the voltage Vd and the target value Vdt. Since the control is performed so that the voltage Vd becomes the target value Vdt, the input / output voltage of the converter is stably controlled in both the charging and discharging operations by simple control. Moreover, since it is a stable and autonomous converter that performs the above-mentioned control even when it does not receive a command from the control unit 7, it is possible to provide a highly reliable system.

  Next, control of the first converter 2 by the control unit 7 will be described in detail with reference to FIGS. 4 and 5. FIG. 4 is a flowchart showing a control flow of the first converter 2 of the control unit 7 during the discharging operation, and FIG. 5 shows a control flow of the first converter 2 of the control unit 7 during the charging operation. It is a flowchart. Note that “START” in the flowcharts of FIGS. 4 and 5 corresponds to a state in which the power conversion apparatus 10 can perform its operation.

  FIG. 3 is a current capacity-voltage characteristic diagram of a typical storage battery 1. As described above, in the present embodiment, the storage battery 1 is a single cell of a lithium ion secondary battery, and the state with the highest voltage is about 4.0 V in the fully charged state, and the state with the lowest voltage is in the end-of-discharge state. It is about 3.0V. Since each storage battery 1 has a capacity variation at the time of manufacture and a variation in deterioration progression during long-term operation, the battery pack 3 has a current capacity as shown in FIGS. It is considered that the storage batteries 1 having different characteristics are mixed. If the same power is discharged from all the storage batteries 1 in which all the first converters 2 are fully charged with respect to the assembled battery 3 having variations from (A) to (C) in FIG. The storage battery 1 of C) reaches the end-of-discharge state the fastest. At that time, since the storage battery 1 of (A) or (B) does not reach the end-of-discharge state, as a result, the storage battery 1 having the characteristics of (A) or (B) is not fully charged to the end-of-discharge state. The battery cannot be used over the entire range.

  In order to compensate for such characteristic variations between the storage batteries 1, the control unit 7 performs the following control on the first converter 2. As described above, the first converter 2 sequentially measures the voltage Vc of the storage battery 1 and transmits the measurement result to the control unit 7 via the communication line 8. The voltage Vc of the storage battery 1 may be measured by the control unit 7 instead of the first converter 2. The flowchart (S1) in FIGS. 4 and 5 reflects the case of this configuration.

  Returning to the description, the control unit 7 calculates the average voltage Vav by summing up the voltages Vc transmitted from all the first converters 2 in the assembled battery 3 and dividing the result by the number of the storage batteries 1 (in the flowchart of FIG. 4). “S2”), the magnitude relationship between the voltage Vc and the average voltage Vav of each storage battery 1 is compared. As a result of this comparison, during the discharge operation, the control unit 7 sends an output increase command via the communication line 8 to the first converter 2 to which the storage battery 1 satisfying Vc> Vav is connected (FIG. 4). After “YES in S3” in the flowchart and “S4”), an output reduction command is sent via the communication line 8 to the first converter 2 to which the storage battery 1 satisfying Vc <Vav is connected (the flowchart in FIG. 4). "S6" after "NO in S3" and "YES in S5").

  On the other hand, during the charging operation, the control unit 7 sends an output reduction command to the first converter 2 to which the storage battery 1 satisfying Vc> Vav is connected via the communication line 8 (in “S3” in the flowchart of FIG. 5). Through “YES”, “S4A”), an output increase command is sent via the communication line 8 to the first converter 2 to which the storage battery 1 satisfying Vc <Vav is connected (NO in “S3” in the flowchart of FIG. 5). ”And“ YES in S5 ”and then“ S6A ”).

  When the first converter 2 receives an output reduction command from the control unit 7 via the communication line 8, the first converter 2 decreases the target value Vdt of the voltage (DC bus side terminal voltage) Vd by ΔVdt (ΔVdt> 0). . Here, assuming that the initial target value Vdt is 10V, the target value Vdt is decreased to 9.9V when an output reduction command is received. Further, when the first converter 2 receives an output increase command from the control unit 7 via the communication line 8, the first converter 2 increases the target value Vdt of the voltage Vd by ΔVdt (assuming ΔVdt> 0). Here, assuming that the initial Vdt is 10V, the target value Vdt is increased to 10.1V when an output increase command is received.

  The voltage equalization of the storage battery 1 achieved by performing the above control will be described with reference to FIG. It is assumed that one of the 38 storage batteries 1 has the characteristic (A) in FIG. 3 and the operating point is A1 (assuming that the voltage Va1 of A1 is 3.21 V), and another storage battery 1 is (C). And the operating point is C1 (C1 voltage Vc1 = 3.19V), and the remaining 36 power storage units 1 have the characteristics (B) and the operating point is B1 (B1 voltage Vb1). = 3.20V). In this case, the average voltage Vav of the operating point voltages of the 38 storage batteries 1 is equal to the voltage Vb1. The average voltage Vav at this time is set to Vav1.

  Assuming that the current discharge operation is in progress, the control unit 7 determines that the storage battery 1 having the characteristic (A) satisfies the above-described condition of Vc> Vav, and thus the first converter 2 to which the storage battery 1 is connected. In response, an output increase command is sent. Further, since the storage battery 1 having the characteristic (C) satisfies the above-described condition of Vc <Vav, the control unit 7 sends an output reduction command to the first converter 2 to which the storage battery 1 is connected.

  Initially, if all the first converters 2 have a target value Vdt of the voltage Vd of 10.0 V, the first converter 2 to which the storage battery 1 having the characteristic (A) is connected is based on the output increase command. The target value Vdt is changed to 10.1V. The first converter 2 to which the storage battery 1 having the characteristic (C) is connected changes the target value Vdt to 9.9 V based on the output reduction command. Since the first converter 2 to which the storage battery 1 having the characteristic (B) is connected is Vc = Vav, the target value Vdt is not changed. Since all the terminals DH and DL of the first converter 2 in the assembled battery 3 are connected in series, all the first converters 2 output the same current value from the terminals DH and DL. Therefore, since the electric power discharged from each storage battery 1 by each first converter 2 is proportional to the target value Vdt, the electric power discharged from the storage battery 1 having the characteristic (A) has a target value Vdt of 10.0V to 10. The electric power discharged from the storage battery 1 having the characteristic (C) is reduced by 1% when the target value Vdt is changed from 10.0 V to 9.9 V. Become. Eventually, the storage battery 1 having a voltage higher than the average voltage Vav has a higher discharge power than the other storage battery 1, and the storage battery 1 having a voltage lower than the average voltage Vav has a lower discharge power than the other storage battery 1. If the discharge operation is continued, the operating point of Vav2 in FIG. 3 is eventually reached and the voltages of the storage batteries 1 are equalized. Since the same applies to charging, the description is omitted.

  As described above, the power conversion device 10 is controlled so that the voltages of the storage batteries 1 match even when there are variations in the charge / discharge characteristics of the storage batteries 1. Therefore, a state in which some of the storage batteries 1 reach the discharge lower limit voltage or the charge upper limit voltage earlier and the other storage batteries 1 cannot be used up to the discharge lower limit voltage or the charge upper limit voltage does not occur. The battery can be used over the entire voltage range, and the storage capacity of the storage battery 1 can be utilized to the maximum even after the deterioration of the storage battery 1 has progressed. Moreover, since it becomes difficult to reach the discharge lower limit voltage or the charge upper limit voltage, the progress of deterioration of the storage battery 1 can be slowed and the life can be extended.

  Furthermore, since the increase / decrease in the charge / discharge power of the storage battery 1 is controlled based only on the current voltage value of the storage battery 1, voltage balance control that corrects the variation of each storage battery 1 without having to measure the difference in capacity of each storage battery 1 It can be performed. Specifically, the voltage balance control can be performed only by changing the target value Vdt of the voltage Vd of the first converter 2 based on a command from the control unit 7. Therefore, it is not necessary to perform complicated communication between the control unit 7 and the first converter 2, and the control can be simplified, so that the cost can be reduced. As described above, the output control of each battery is performed by a simple method, and charge / discharge control is performed so that the capacity of each battery can be utilized to the maximum, so that the system depends on the degree of deterioration of each battery and the variation in capacity. It is possible to provide a power conversion device that does not shorten the entire life.

  As described above, the voltage Vc of the storage battery 1 may be measured by the first converter 2 and the measurement result may be transmitted to the control unit 7 via the communication line 8 or It may be configured to be directly measured by the control unit 7. Further, the processing performed by the control unit 7 described above may be provided as a function in a control circuit that controls the first converter 2 or the second converter 4 itself, or an actual circuit. Instead, it may be virtual.

  When the control unit 7 is virtual, the control unit 7 includes a CPU (central processing unit) that executes instructions of a control program for realizing each function, a ROM (read only memory) that stores the program, and the above A RAM (random access memory) for expanding the program, a storage device (recording medium) such as a memory for storing the program and various data, and the like are provided. An object of the present invention is a recording medium on which a program code (execution format program, intermediate code program, source program) of a control program of the control unit 9 which is software that realizes the above-described functions is recorded so as to be readable by a computer. This can also be achieved by supplying the control unit 9 and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  The control unit 7 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Further, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention individually controls the output so that the converters connected to each battery asymptotically approach a common battery voltage target value, so that all batteries can be used in the entire voltage range from the end of discharge to the end of charge, Depending on the degree of deterioration of each battery and variations in battery capacity, it is possible to maximize the use of all battery capacities without being limited by the life of the battery with the least capacity. The present invention can be suitably used for a power conversion device for a storage battery that converts DC or AC power generated by power generation into AC power having a commercial frequency.

It is a block diagram which shows the principal part structure of the power converter device which concerns on embodiment of this invention. (A) is a circuit diagram which shows the specific structure of a 1st converter, (b) is a circuit diagram which shows the specific structure of a 2nd converter. It is a current capacity-voltage characteristic view of a typical storage battery. It is a flowchart which shows the control flow of the 1st converter of the control part at the time of discharge operation. It is a flowchart which shows the flow of control of the 1st converter of the control part at the time of charge operation.

Explanation of symbols

1 Storage battery (electric storage means)
2 First converter (first conversion means)
4 Second converter (second conversion means)
5 Power system (power source)
6 DC bus 7 Control section (control means)
10 Power converter

Claims (6)

A power conversion device that converts power from a plurality of storage means capable of charging and discharging and supplies the power to a power source,
The voltage value of each power storage means is measured, the average value of all the measured voltage values is calculated, the calculated average value and the voltage value of each power storage means are respectively compared, and each of the above-described values based on the comparison result Charging / discharging control means for controlling charging and discharging of the power storage means,
The power conversion device has a charge operation mode for charging the power storage means and a discharge operation mode for discharging from the power storage means,
The charge / discharge control means includes
In the discharge operation mode, among the power storage means, a discharge output increase control for increasing the discharge power of the power storage means in which the voltage value of the power storage means is greater than the average value, and the voltage value of the power storage means is the average Performing at least one of the output reduction control during discharge to reduce the discharge power of the power storage means smaller than the value,
In the charging operation mode, among the power storage means, a charge output reduction control for reducing the charging power of the power storage means whose voltage value is higher than the average value, and the voltage value of the power storage means is the average Perform at least one of the output increase control during charging to increase the charging power of the power storage means smaller than the value,
By adjusting the pulse width of the drive pulse that is provided for each power storage unit and drives the switch element, the charging current to each power storage unit and the discharge current from each power storage unit are controlled to control each power storage unit. A first power conversion means that is a switching converter that performs charging and discharging;
An output increase command is given to the first power conversion means in the output increase control and discharge output increase control, and the first power conversion means in the discharge output decrease control and charge output decrease control. Control means for controlling the first power conversion means by giving an output reduction command to
The power converter is
DC bus,
A second power conversion means connected to the DC bus and the power source for converting power to and from the power source; and
The first power conversion unit has a power storage unit side terminal connected to the power storage unit and a DC bus side terminal connected to the DC bus, and the DC bus side terminal voltage matches a target value. Control the pulse width as above,
The direct current bus side terminals of the first power conversion means are connected in series with each other and connected to the direct current bus . The first power conversion means includes:
In the discharge operation mode, when the measured value of the DC bus side terminal voltage is larger than the target value, the pulse width of the switch element is decreased, and when the measured value of the DC bus side terminal voltage is smaller than the target value, Increase the pulse width of the switch element,
In the charging operation mode, when the measured value of the DC bus side terminal voltage is larger than the target value, the pulse width of the switch element is increased, and when the measured value of the DC bus side terminal voltage is smaller than the target value, 2. The power conversion device according to claim 1 , wherein the DC bus side terminal voltage is controlled to be the target value by reducing a pulse width of the switch element. When the first power conversion means receives the output increase command from the control means, the first power conversion means updates the target value of the DC bus side terminal voltage to a value increased from an initial value, and decreases the output from the control means. power converter according to claim 1 or 2 when receiving the instruction and updates the value reduced the target value from the initial value. The power source is a commercial power system,
The power converter according to any one of claims 1 to 3 , wherein the second power conversion means is a grid-connected inverter circuit. Claims 1 to 4, one power converter apparatus control program for operating a computer as a control means of the power converter according to one of. The computer-readable recording medium which recorded the power converter control program of Claim 5 .

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