JPH0713401Y2 - Power storage battery power converter - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a power conversion device for accommodating power between a power storage battery and a system power supply, and in particular, reactive power compensation when the battery is completely discharged. Regarding control.

B. Outline of the Invention The present invention is to completely discharge the battery to the system power source side by the separately-excited complete discharge device, and by performing reactive power compensation control of the self-excited AC-DC converter for power interchange during complete discharge, This is to suppress the reactive power outflow to the side.

C. Conventional technology Electricity demand fluctuates greatly even during the day, and the load at night is significantly lower than at daytime. Therefore, the electric power is stored at the time of light load, and the stored electric power is released at the time of peak load, so that the electric power system equipment can be efficiently used by leveling the load. Here, a secondary battery is adopted for power storage, and in a conventional lead battery, power is repeatedly charged and discharged with a system power supply by an ordinary AC / DC converter, but the battery voltage drops due to overdischarge. If it is too long, the battery life will be significantly shortened, so that the battery can only be used within the range of the charge / discharge end voltage. However, in a secondary battery that uses zinc as an active material of the cathode (for example, a zinc bromine battery), when the charge and discharge are repeated to some extent, a protrusion called a dendrite is generated on the cathode, which deteriorates the battery performance. By completely discharging the secondary battery, Dentrite is dissolved and the cycle life of the battery is extended.

The battery requiring the complete discharge cannot be voltage controlled until the complete discharge in the conventional AC-DC converter, so that it is used as a power converter having a separate complete discharge device as shown in FIG. In the figure, the self-excited AC / DC converter 1 has a main circuit configuration in which a GTO thyristor and a flywheel diode are bridge-connected in an anti-parallel connection, and DC power from the power storage battery 2 is passed through the changeover switch 3 and the smoothing capacitor 4. The AC power is converted into AC power having a frequency and voltage that match the system power supply, and this AC power is exchanged with the system power supply 8 through the transformer 5, the interconnection reactor 6, the harmonic suppression filter 6A and the switch 7. Further, the AC / DC converter 1 converts electric power from the system power supply 8 into DC and stores it in the battery 2.

On the other hand, the complete discharge device 14 for the battery 2 includes two sets of thyristor bridges 1 from the changeover switch 3 via the DC reactor 9.
Connected to the anti-parallel circuit of 0,11, thyristor bridge 10,1
System power supply 8 via transformer 12 and switch 13 on the AC side of 1
Connected to. This complete discharge device 14 switches the changeover switch 3 from the state shown in the figure to complete discharge of the battery 2, performs constant current discharge by the reverse conversion operation of the thyristor bridge 11, and charges the battery 2 to the rated voltage after complete discharge. The initial charge is performed by the forward conversion operation of the thyristor bridge 10.

Figure 3 shows a power storage battery 2 in a 500KW class power storage system.
The charge-discharge time chart of is shown. In the figure, until the time t ₁ represents the power interchange period by alternating current-and-direct current conversion device 1, from time t ₂
until t ₆ indicated complete discharge and duration of the initial charging. Of these, a full discharge period is the inverse conversion operation of the thyristor bridge 11 in time t _2, the from time t ₃ to the reverse charged by the forward transform operation to maintain a negative voltage (about -50 V), the time t ₄ when the elapse of a predetermined period of time Then, the thyristor bridge 11 is stopped to complete the complete discharge.

Next, during the initial charging period, at time t ₅ , the thyristor bridge 10
In the reverse conversion starts to charge the battery 2, to increase the battery voltage in the reverse discharge until the specified voltage, complete the specified voltage after the initial charging stop thyristor bridge 10 at time t ₆ was charged in the order conversion To do.

During the complete discharge period and the initial charge period, the changeover switch 3 is switched to the complete discharge device 14 side, at the same time, the switch 7 is opened and the switch 13 is opened, and the AC / DC converter 1 is stopped. .

D. Problem to be Solved by the Invention In the conventional device, during operation of complete discharge and initial charge of the battery, since the thyristor bridges 10 and 11 are separately excited, a large delayed reactive power flows to the system power supply 8. , There was a problem of becoming a power converter with a poor power factor.

The reactive power is most large reversed charging period of time T ₃ through T ₄ of FIG. 3, a DC voltage 50 V, the reactive power of a DC current 200A is as follows.

The DC side voltage E _d of the thyristor bridges 10 and 11 is expressed as E _d = k cos α K; constant, α; thyristor control angle, and the control angle α ₁ when the maximum value of the DC voltage (battery voltage) is 1120 V Is 10 °, the control angle α ₂ for a DC voltage of 50 V is α ₂ = cos ⁻¹ {50/1120 × cos α ₁ } = 87.5 °. Further, since the expressed reactive power Q ₂ is the active power P ₂ and _{Q 2 = P 2 × tanα 2} , Q 2 = 50 (V) × 200 (A) × tanα 2 = 229 (KVar) , and the very Large reactive power flows out to the system power supply 8 side.

The object of the present invention is to suppress the reactive power outflow to the grid due to the complete discharge operation of the battery.

E. Means and Actions for Solving the Problem In order to achieve the above-mentioned object, the present invention provides a self-excited AC / DC converter that allows power to be exchanged between a power storage battery that requires a complete discharge and a system power supply, and In a power conversion device equipped with a complete discharge device for performing a complete discharge and an initial charge of the battery between a battery and a system power supply, reactive power generated during operation of the complete discharge device is converted into reactive power of the AC / DC converter. The reactive power control means for compensating by the power compensating operation is provided, and the AC / DC converter is operated as the reactive power compensator during the operation of the complete discharge device, and the AC / DC converter compensates the reactive power generated by the complete discharge and the initial charge.

F. Embodiment FIG. 1 is a device configuration diagram showing an embodiment of the present invention. In the figure, the self-excited AC / DC converter 15 is the transformer of FIG.
5, The reactor 6, the filter 6A, and the AC / DC converter 1 have the same configuration. The complete discharge device 16 has the same structure as the DC reactor 9, the thyristor bridges 10 and 11 and the transformer 12 shown in FIG. In addition, these control devices are incorporated respectively.

The reactive power detection circuit 17 detects the system voltage 8 from the detected voltage and current phase during the complete discharge and initial charge operation of the complete discharge device 16.
The reactive power Q output to is detected. On the other hand, the reactive power detection circuit 18 detects the reactive power Q ′ output from the AC / DC converter 15 to the system power supply 8. The control circuit 19 controls the reactive power output of the AC / DC converter 15 with the detected reactive power Q of the detection circuit 17 as a target value and the detected reactive power Q ′ of the detection circuit 18 as the feedback amount.

In the above configuration, the changeover switch 3 is changed over to the complete discharge device 16 side for complete discharge and initial charge of the battery 2, and the switch 13
In addition to turning on, the switch 7 is turned on to turn the AC / DC converter 15
To operate the reactive power compensation. That is, the detection circuit 17 detects the reactive power that the complete discharge device 16 tries to flow to the system power supply 8 during the complete discharge and the initial charge of the battery 2, and the reactive power Q ′ opposite to the detected reactive power Q is subjected to AC / DC conversion. The control circuit 19 controls the output of the device 15.

In this case, the AC / DC converter 15 is controlled by constant voltage control in which the capacitor 4 is a DC power source and the voltage thereof is kept constant.
Therefore, the control circuit 19 determines the voltage of the capacitor 4 and the set voltage.
Obtain the deviation signal from V _pc and perform reactive power control. Further, the AC / DC converter 15 has sufficient power processing capacity for the original power interchange, and has a power processing capacity higher than that of the 500 KW class power converter, which is sufficient for the above-mentioned reactive power amount of 229 KVar. With the ability to compensate.

In addition, the reactive power compensation operation of the AC / DC converter 15 is not limited to the complete discharge and initial charge of the battery, and the complete discharge device 16 is stopped for a long time (t ₄ to t _{5 in} FIG. 3). Then, when the loss of the AC / DC converter 15 becomes excessive, the compensating operation may be stopped at time t ₄ . In this case, the reactive power compensation cannot be performed during the initial charging period (t ₄ to t _{6 in} FIG. 3), but this period is short in time and the thyristor control angle α of the complete discharge device 16 is also on average. Since it becomes large, the amount of reactive power also becomes small, and the influence on the system power supply 8 is small.

Further, the reactive power compensation operation of the AC / DC converter 15 is performed by the device 15
Can also be used in the case of performing the power interchange operation, which is realized by giving the set value ΔQ instead of the detection amount Q of the detection circuit 17. Further, in addition to the reactive power compensation from the complete discharge device 16, a set value ΔQ can be given to compensate for the reactive power of the system power supply 8 itself.

G. Effect of the Invention As described above, according to the present invention, the reactive power generated by the complete discharge device is compensated by the AC-DC converter.
The large reactive power generated when the battery is completely discharged does not flow out to the system power supply, and the reactive power detection and its control circuit are added in terms of the device configuration.

[Brief description of drawings]

FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention, FIG. 2 is a conventional circuit diagram, and FIG. 3 is a charge / discharge time chart of a power storage battery. 1 ... AC / DC converter, 2 ... power storage battery, 8 ... system power supply,
15 ... Self-excited AC / DC converter, 16 ... Complete discharge device, 17,18 ...
Reactive power detection circuit, 19 ... Control circuit.

Claims (1)

[Scope of utility model registration request] 1. A self-excited AC / DC converter that allows electric power to be exchanged between a power storage battery that requires a complete discharge and a system power supply, and complete discharge and initial charging of the battery between the battery and the system power supply. In a power conversion device including a complete discharge device for performing the above, a reactive power control means for compensating the reactive power generated during operation of the complete discharge device by a reactive power compensation operation of the AC / DC converter is provided. Power storage battery power conversion device.