RU120291U1 - BACK-UP POWER SUPPLY SYSTEM WITH BOOSTER CIRCUIT - Google Patents

Abstract

A backup power supply system based on a supercapacitor with a booster circuit, containing a generator and a load, characterized in that an energy storage device on a supercapacitor, a booster circuit and a charge circuit from the generator are introduced; the output of the charging circuit and the input of the booster circuit are connected to the supercapacitor, the input of the charging circuit being connected to the generator, and the output of the booster circuit to the load, while a diode is connected between the generator and the load.

Description

The utility model relates to electrical devices for converting direct current into direct current and is intended for use in electric networks or similar power supply systems for converting input direct current energy into output energy of a desired type, as well as controlling or regulating such devices and can be used in vehicle power supply systems, sources uninterruptible power supply, renewable energy installations based on solar cells or wind generators.

A device "Boost Converter" [1] containing two out-of-phase booster converters is known.

The characteristics of this device allow to increase the ultimate power by a factor of two compared to a single circuit without compromising efficiency and improving the quality of the output energy.

However, the use of this circuit in relation to the storage system on supercapacitors is not provided.

The closest technical solution is the "Device for controlling the battery charge" [2], in which the battery is used as a drive.

However, in the prototype, a battery drive is not able to efficiently give and receive large powers; characterized by limited resource charge-discharge cycles and service life; requires maintenance; poorly tolerates operation at low temperatures.

The purpose of the utility model is to increase the efficiency of the backup power system, which is characterized by: the ability to return and receive high power; significantly longer charge-discharge cycle life and service life; without the need for maintenance and non-critical to operating temperature.

The technical result is achieved by replacing the battery with a supercapacitor, to which a booster circuit and a charge circuit from the generator are added.

The essence of the technical solution is as follows:

The backup power system on the supercapacitor with a booster circuit contains a generator and a load, in addition, an energy storage on the supercapacitor, a booster circuit and a generator charge circuit are additionally introduced. The output of the charge circuit and the input of the booster circuit are connected to a supercapacitor, with the input of the charge circuit connected to the generator and the output of the booster circuit to the load. A diode is connected between the generator and the load.

Figure 1 shows the electrical circuit of a backup power device on a supercapacitor with a booster circuit, including: an energy storage device on a supercapacitor 1, a booster circuit 2, a charge circuit from a generator 3 and a diode for direct energy transfer from a generator to a load 4. Figure 2 shows the time diagrams of the booster circuit 2. Figure 3 shows graphs of the dependence of the efficiency on the output power of the booster circuit 2.

The device operates as follows.

Suppose that in the circuit of the charge from the generator 3, the generator G ceases to generate electrical energy. In this case, the transistor VT _{1 is} closed, the charge circuit from the generator 3 is disconnected from the generator and the booster circuit 2 starts working, the task of which is to maintain a constant load voltage U _n as the energy storage on the supercapacitor 1 is discharged. If the voltage of the energy storage on the supercapacitor is 1 U ₀ greater than the minimum operating voltage U _n , the transistor VT _{2 of the} booster circuit 2 is closed, and direct energy is transferred to the load by direct current through an inductive coil and an open diode VD ₂ . Due to the direct voltage drop across the diode and the active loss of the coil, a slight power loss occurs. Direct transmission efficiency of more than 95%. When the load voltage U _n decreases to a critical level, the typical PWM controller chip controlling the operation of the booster circuit 2 begins to generate periodic voltage pulses U _y2 with automatically changing duty cycle. The control pulses are applied to the VT ₂ gate (powerful MOSFET transistor), as a result of which the output voltage is kept constant by the booster circuit 2, both when the voltage U ₀ decreases and when the load resistance changes.

Figure 2 shows the timing diagrams of the operation of the booster circuit 2. On the interval of duration τ _{and the} control pulse U _y2 there is an accumulation of energy in the coil L - inductive energy storage (INE), the current i ₂ reaches the value i _L. For the efficiency (efficiency) of energy storage, the formula is obtained:

Here, i _m = U ₀ / R, t _L = L / R is the time constant of the circuit, R is the total active resistance of the INE charge circuit. For a fixed charge time t, the highest efficiency is obtained for a zero initial current i ₀ . From formula (1) it is seen that the maximum efficiency close to unity is achieved at t = τ _and << τ _L. In this case, the charge current can be estimated from the expression:

i _L ≈U ₀ τ _and / L,

and the energy of INE from the expression:

Note that when public key ₂ VT voltage across it is close to zero, diode VD switch ₂ is closed, power to the load to provide a charged voltage U _n capacitor C _n.

At the end of the control pulse, VT ₂ closes, the current i _{2 of the} inductive coil, while maintaining continuity, induces an EMF of positive polarity, which opens the diode UD ₂ , and energy is transferred from the source U ₀ and the coil to the load and capacitor C _n . In this case, the capacitor is charged to a voltage U _n greater than the voltage of the source U ₀ , and the inductance current i ₂ is oscillatory in nature and has a constant component. When the current passes through zero at time τ, the key VD _{2 is} automatically closed. In this case, all the energy of the INE is transferred to the capacitor and the load, which is disconnected from the source U ₀ for the time T-τ. The load is powered by a charged capacitor, which is slightly discharged over the T-τ interval. At the end of the next control pulse, another portion of energy is transferred to the load and capacitor. Since the frequency of the control pulses is high enough, after a short time, a constant pulsating voltage U _n > U _{0 is} established at the load, which can be adjusted by changing τ _and (or duty cycle) of the control pulses. With increasing τ, _{both the} voltage and load power increase.

The constant component of the inductance discharge current depends on the voltage U ₀ , the load resistance R _n and the value of i _L. With decreasing i _L , the INE current may not pass through zero, the key VD ₂ will not close, and the circuit will operate in continuous current mode i ₂ . In this case, the efficiency (1) of the INE charge decreases. Due to the fact that the small current i _L makes a small contribution to the output power, the overall efficiency of the booster circuit decreases slightly. Much more important to provide discontinuous current mode at the maximum power output, when τ _{and the} maximum contribution Ine (2) to output the stored energy and also a significant decrease maximal η _L (1) will also lead to a significant reduction in the total efficiency of the booster circuit 2. In discontinuous mode currents must satisfy the condition:

An algorithm for calculating the dynamics of booster circuit 2 is developed, which allows one to calculate the time of energy transfer to the load τ, as well as the load voltage U _n and the energy conversion efficiency. To calculate the efficiency η, the formula is obtained:

where U _cf is the calculated average load voltage.

Implemented a prototype booster circuit 2 (figure 1). The coil is wound on a ring core made of magnetodielectric wire from the Litz wire. The load is low resistance, R _H ≈1 Ohm. The transistor switch VT _{2 is} implemented on a powerful MOSFET transistor IRFP044N. The key was controlled by a pulse generator through a repeater on the KP-901 transistor. As a key VD ₂ , a Schottky SBL3040PT diode was used. The equivalent of a supercapacitor is a laboratory linear power supply operating in voltage stabilization mode. To reduce the effect of equivalent series resistance, the filter capacitor C _{n is} implemented by parallel connection of capacitors of lower capacity. The ultimate output power in the experiment is limited by the ultimate current of the laboratory source. The maximum power in the calculation is limited by maintaining the regime of rupture currents (3). The results of the experiment ("□") and calculation (4) of the efficiency of the booster circuit for three voltage values U ₀ : 1-7B, 2-9B and 3-11B are shown in Fig.3. The circuit has an acceptable efficiency at a sufficiently high ultimate output power, limited by condition (3). It is possible to double the output power while reducing the ripple factor of the output voltage by half (keeping the efficiency constant) by using the parallel connection of two identical booster circuits 2 to the total load. The circuits operate at the same frequency and are started alternately with a time shift of half a period. The source efficiency can be increased by using elements of electronic keys with less losses, using a larger cross-section wire in the inductance winding and optimizing the arrangement of power circuit elements.

Consider the charge circuit from the generator 3, shown in figure 1. The transistor VT _{1 is} controlled by a PWM controller with a variable duty cycle S and allows you to adjust the charge process of the energy storage on supercapacitor 1. The average voltage U _x depends on the duty cycle:

U _x = E / S

and should vary from the initial value of the voltage of the energy storage device on the supercapacitor 1 U ₀ to the value of the EMF E generated by the generator G as S → 1. Through the energy storage on the supercapacitor 1 and the shunt R flows the average charging current i ₁ :

i ₁ = (U _x -U ₀ ) / R.

If the control of the transistor is organized in such a way (changing the duty cycle S) so that the average charging current does not change, then the charge efficiency of the energy storage on the supercapacitor 1 will be determined by the expression:

Here, τ = R _p C is the charge time constant, R _p is the total active resistance of the charge circuit. If the charge time t _{s is} significantly longer than the time constant, the charge efficiency (5) will be close to 1. The PWM key controller VT ₁ controls the duty cycle in such a way as to ensure a constant voltage (U _x -U ₀ ) on the shunt R. Thus, the voltage U _{0 of the} energy storage on the supercapacitor 1 during the charge will linearly increase from the initial value to a maximum close to the EMF of the generator E, after which the charge ceases.

Consider the operation of the full electrical circuit of the backup power device shown in figure 1. If the generator G works, generating a rated voltage E, the diode 4 (VD ₁ ) is open and this voltage is supplied to the load R _n . In this case, the load voltage exceeds the voltage at which the PWM controller of the booster circuit 2 is started, the transistor VT ₂ and the diode VD ₂ are closed and the booster circuit 2 is turned off. There is a direct transfer of energy from the generator G to the load R _n . If the voltage U _{0 is} less than the maximum, the energy storage device on the supercapacitor 1 is simultaneously charged through the charge circuit from the generator 3 to a maximum value close to E. When the generator D is not working, diode 4 (VD ₁ ) is closed, the diode key VD _{2 is} opened and direct energy transfer by the booster circuit 2 from the energy store on the supercapacitor 1 to the load. When the voltage decreases to a threshold value, the PWM controller of the booster circuit 2 is launched, control pulses are supplied to the VT ₂ gate, and the load voltage is kept constant until the energy storage on the supercapacitor 1 is discharged to a predetermined critical voltage, for example, to the value E / 2. After that, the booster circuit 2 is turned off and the power transfer is stopped. The critical voltage of the energy storage device on supercapacitor 1 should ensure that generator G is restarted. When the generator D is turned on again, its energy is transferred to the load directly through diode 4 (VD ₁ ) and the energy storage device is charged on supercapacitor 1, and booster circuit 2 is turned off.

Information sources:

1. Patent US 2007/0096700 A1 Boost Converter

2. Patent RU No. 2293415 dated February 10, 2007. A device for controlling the battery charge (prototype).

Claims (1)

A backup power system on a supercapacitor with a booster circuit comprising a generator and a load, characterized in that the energy storage on the supercapacitor, a booster circuit and a charge circuit from the generator are introduced; the output of the charge circuit and the input of the booster circuit are connected to a supercapacitor, with the input of the charge circuit connected to the generator and the output of the booster circuit connected to the load, while a diode is connected between the generator and the load.