JPH07110111B2 - Power storage battery AC / DC converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an AC / DC converter for a power storage battery that requires a complete discharge.

B. Summary of the Invention The present invention relates to an AC-DC converter that allows power to be exchanged between a power storage battery and a system power supply, and charges and discharges a battery for power interchange and a battery charge and discharge for complete discharge. By using a single converter, it is possible to reduce the size and cost of the device.

C. Conventional technology AC / DC converters used for load leveling with power storage batteries and peak cut systems are self-exciting type self-exciting devices with the progress of high withstand voltage and large current in self-extinguishing type power semiconductor devices. Voltage type has become common. The basic structure is shown in FIG.

In the figure, the self-excited voltage type AC / DC converter 1 has a main circuit configuration in which a GTO thyristor and an anti-parallel arm of a flywheel diode are bridge-connected, the DC side is connected to the power storage battery 2, and the AC side is the interconnection reactor 3. Is connected to the system power supply 4 via.

In this configuration, the AC / DC converter 1 controls the crest value / phase of the fundamental wave voltage at the output terminal A on the AC side to slightly change the crest value / phase of the current flowing through the interconnection reactor 3 by the control. Change. Therefore, in addition to the charge / discharge power control of the battery 2, it is possible to control the reactive power of the phase advancing / lagging as a phase adjusting device.

D. Problems to be Solved by the Invention In the conventional AC / DC converter, in the case of the power storage battery that becomes the DC power source, the life is significantly shortened when the battery voltage drops too much due to over-discharging like the lead battery. Some batteries can only be used within the voltage range. On the other hand, there are some batteries, such as a zinc bromine battery, in which, when charging and discharging are repeated at a certain battery voltage or more, a projection called a dendrite is generated on the electrode surface to deteriorate the battery performance.

In such a battery, in order to remove the dendrite, discharging (complete discharging) is periodically performed until the battery voltage becomes zero.
When a battery that requires this complete discharge is used as the DC power supply for a conventional AC / DC converter, the voltage-type AC / DC converter cannot be controlled if the DC voltage drops below a certain value from the operating principle. A separate device for pre-charging to fully discharge and charge to a voltage at which the AC / DC converter can operate is required. As an apparatus for this purpose, for example, there is a separately-excited power conversion apparatus, but in any case, there is a problem that such an apparatus is required and the whole system becomes large and the cost becomes high.

An object of the present invention is to provide an AC / DC converter capable of reducing the size and cost of the device while using a DC power source as a power storage battery that requires complete discharge.

E. Means for Solving the Problem and Its Action The present invention, in order to achieve the above object, in the AC-DC converter for performing power interchange between the power storage battery and the system power source that require complete discharge, A charging / discharging changeover switch with a chopper function that switches between discharging and charging from the battery and controlling the charging / discharging current by controlling the conductivity, and a system power supply provided with a DC reactor in series between this switching switch and the system power supply. A self-excited current type AC / DC converter that controls the phase difference between the AC / DC converter and the AC / DC converter to convert electric power between the battery and the system power supply, and a phase difference control of the AC / DC converter or conduction of a changeover switch. The battery is provided with a control means for lowering the rate to perform complete discharge of the battery and subsequent initial charge control, to perform normal charging / discharging of the battery by controlling the direct current, and to control the direct current or the phase difference to Performs all the discharge and precharge news performs active power, reactive power control.

F. Embodiment FIG. 1 is a device configuration diagram showing an embodiment of the present invention. In the figure, the power storage battery 2 is provided with a self-excited current type AC / DC converter 6 via a charge / discharge changeover switch 5 having a chopper function.
Connected to the DC side of. The changeover switch 5 is composed of GTO thyristors G _P and G _N and diodes D ₁ and D ₂ and controls the conductivity of the thyristors G _P and G _N from the battery 2 to the AC / DC converter 6.
The discharge current to and from the charge current. The AC / DC converter 6 is a DC reactor DCL and a GTO thyristor G _U , G _V , G _W , G
_It is configured by a bridge connection of _X , G _Y , and G _Z , and performs DC-AC conversion for power supply to the system power supply 4 side and AC-DC conversion for power reception from the system power supply side.

The control of the changeover switch 5 and the AC / DC converter 6 is performed by the gate control by the control device 7, and the changeover switch 5 controls the DC power supply I _DC by the conductivity control.
The forward / backward operation control is performed by the phase angle control.

With such a configuration, the changeover switch 5 and the AC / DC converter 6
Performs not only normal charging / discharging of the battery 2 but also complete discharging and reactive power control. Further, the changeover switch 5 is used to provide a control function for making the direct current I _{DC an} arbitrary constant value. According to this control, the ratio (control rate) M of the effective value I _RMS of the fundamental wave of the current flowing between the system power supply 4 and the converter 6 and the direct current I _DC is set to I _RMS / I _DC = M constant. In addition, the current control is PWM control to reduce the harmonic components of the current flowing into the system power supply side. It also controls the phase difference φ between the fundamental wave component of the current from the converter 6 and the phase voltage of the system. With this control and the above-mentioned current control, the active power P and the reactive power Q supplied to the grid by the system are P = 3V _RMS (M · I _DC ) cosφ Q = 3V, where _RMS is the effective value of the phase voltage of the grid. _RMS (M · I _DC ) sin φ, DC current I _DC control and phase difference φ control −90 ° <φ <90 ° discharge 90 ° <φ <270 ° (= −90 °) Charging This enables arbitrary P and Q control.

The control method of I _DC during charging and discharging will be described below.

[During discharge] The converter controls the E _{DC in} Fig. 1 so that E _DC > 0 and E _B > E _DC , so that the thyristor G _{N is} continuously turned on and the thyristor G _{P is set} to PWM or PFM. The I _DC can be controlled to be constant by the control (the pulse width is made constant and the period thereof is controlled) or the control in which they are used together. That is, when G _P is on, I _DC is battery 2
It flows from the anode → G _P → DCL → bridge → G _N → cathode of the battery, so the change ΔI _DC of I _DC can be approximately expressed as the following equation.

Δt is the ON time of G _P L is the inductance value of DCL where E _B > E _DC , so ΔI _DC becomes positive and I _DC increases.

Conversely, when the thyristor G _P is off, I _DC is DCL → bridge →
G _N → D ₁ → DCL and circulation (G _N and D1 is the operation of the flywheel diode) and change in the I _DC from flowing ΔI
_DC can be approximately expressed as the following equation.

Since E _DC > 0 here, ΔI _DC becomes negative and I _DC decreases. Therefore, it can be seen that I _DC can be controlled by repeatedly turning G _P on and off.

The Charging time] converter, E _DC <0 a and E _B> | E _DC | By controlling so as to, and G _N continuous off, the same control as described above the G _P, I _DC Is controlled to be constant.
That is, when G _P is off, I _DC is the battery cathode → D ₁ → DCL →
Bridge → O ₂ → Flows from battery anode to I _DC change ΔI
_DC can be approximately expressed as the following equation.

Here, since E _DC <0 and E _B > | E _DC |, the numerator in the above formula becomes negative and the battery is charged, but I _DC is reduced due to the battery voltage. When G _P is on, I _DC flows from DCL → bridge → D2 → G _P → DCL, so the change in I _DC ΔI _DC can be approximately expressed by the following equation.

Since E _DC <0 here, I _DC is increased. Therefore, in this case as well, it can be seen that I _DC can be freely controlled by repeatedly turning G _P on and off.

In the above explanation, the ON / OFF state of G _N is kept constant and G _P
Was controlled, but the reverse is the same.

[Complete discharge and preliminary charge] In this state, E _B is 0
≦ E _B ≦ E _BMIN Within the range. Here, E _BMIN is a phase difference φ of 0 ° and 18 with the control rate M of the converter being constant.
| E _DC when controlled to 0 ° (that is, charge / discharge at power factor 1)
Is almost equal to |. Therefore, when E _B is within the above range, P and Q cannot be controlled arbitrarily. At this time, if φ is gradually brought to 90 ° or −90 °, or if the control rate M of the converter is lowered, | E
It becomes _DC | → 0, and complete discharge and preliminary charge can be performed with the same control as the above discharge and charge.

G. Effects of the Invention As described above, according to the present invention, the charging / discharging changeover switch having the chopper function and the self-excited current type AC / DC converter are provided,
Since the system is configured to perform full discharge / precharge in addition to charge / discharge of the battery by charge / discharge current control and phase difference control, a system configuration with two devices for normal charge / discharge and full discharge / precharge of the battery is provided. Compared with this, it is possible to reduce the size of the device and reduce the cost. Moreover, functionally, simultaneous control of active power and reactive power is possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional AC / DC converter. 2 ... Power storage battery, 4 ... System power supply, 5 ... Charge / discharge switch with chopper function, 6 ... AC / DC converter, 7 ...
…Control device.

Claims (1)

[Claims] 1. In an AC / DC converter that allows power to be exchanged between a power storage battery that requires a complete discharge and a system power supply, the charge and discharge current is controlled by switching discharge and charge from the battery and controlling the conductivity. A charging / discharging changeover switch with a chopper function, and a DC reactor installed in series between this changeover switch and the system power supply, the phase difference with the system power supply is controlled, and the power conversion is performed in both directions, and the battery A self-excited current type AC / DC converter that exchanges electric power with a system power supply, and phase difference control of the AC / DC converter or control for performing complete discharge of the battery and subsequent initial charge control by lowering the conductivity of a changeover switch. An AC / DC converter for a power storage battery, which is provided with a means.