CN214590681U

CN214590681U - Direct current power supply system with abnormal protection mechanism

Info

Publication number: CN214590681U
Application number: CN202120633536.2U
Authority: CN
Inventors: 张干; 迟旭东; 金海江; 孙明红; 陆成海; 李悦; 钟士超; 初洪祥; 纪涛
Original assignee: Yantai Dongfang Yokelin Electonic Co ltd
Current assignee: Yantai Dongfang Yokelin Electonic Co ltd
Priority date: 2021-03-29
Filing date: 2021-03-29
Publication date: 2021-11-02
Anticipated expiration: 2031-03-29

Abstract

The utility model provides a DC power supply system who possesses unusual protection mechanism, this system are by power correction charge module, super capacitor module, boost module and management and control module and constitute, wherein the input of power correction charge module passes through AC/DC converter and is connected with alternating current supply circuit, does the super capacitor module power supply, super capacitor module's input with power correction charge module connects, the output with boost module connects, and it combines boost module is for the direct current side primary equipment and the secondary equipment power supply that possess the power supply demand, by the management and control module is according to the operation of each module of the state information control of collection. By adopting the power supply system, the risk that the direct current demand side is damaged in a large range when the power supply system is abnormal can be avoided, even if the power supply system is powered off or strong voltage fluctuation is met, the protection circuit can be controlled to work in time, primary equipment influencing the demand side is avoided, a high-power-factor charging circuit is adopted, and the cost and the occupied space of the super capacitor are saved.

Description

Direct current power supply system with abnormal protection mechanism

Technical Field

The utility model relates to a power grid power supply system optimizes technical field, especially relates to a DC power supply system who possesses abnormal protection mechanism.

Background

The transformer substation is an indispensable part of an electric power system, and has been developed together with the electric power system for more than 100 years, and in the development process of more than 100 years, the transformer substation has great changes in aspects such as construction sites, voltage levels, equipment conditions and the like; in the voltage class, with the development of power technology, a small power grid transmission mode which originally uses a small number of 110kV and 220kV transformer substations as hub transformer substations and 35kV as terminal transformer substations is gradually developed into a large power grid transmission mode which uses extra-high voltage 1000kV transformer substations and 500kV transformer substations as hub transformer substations and uses 220kV and 110kV transformer substations as terminal transformer substations; in the aspect of electrical equipment, primary equipment is mainly open outdoor equipment and gradually develops into a totally-enclosed gas combined electrical appliance (GIS) and a semi-enclosed gas combined electrical appliance (HGIS); secondary devices have evolved from early transistor and integrated circuit protection to microcomputer protection.

The direct current power supply system is an important component of a transformer substation, is a power supply of secondary systems such as a relay protection control device, an automation device, a high-voltage circuit breaker switching-on and switching-off mechanism, communication, metering, emergency lighting and the like, and mainly comprises a storage battery pack and a rectifying device, wherein the input end of the storage battery pack is connected with an alternating current power supply end, and the output end of the storage battery pack is connected with a direct current bus or a load. Under the normal operation condition, the direct current power supply system is supplied by station alternating current through the rectifying device, and when sudden alternating current is lost, the station direct current power supply system is supplied with power by the storage battery pack, so that the storage battery pack becomes the only direct current power supply. However, the storage battery pack is used as a standby power supply, the following considerable potential safety hazards generally exist, because the maintenance amount of the battery pack is huge, a large number of battery packs are not maintained in place every year in the existing system, the operation conditions of the battery packs in some stations are severe and basically have no capacity, and the operation and inspection personnel cannot monitor and know the situation in time, under the situation, the voltage of a direct current bus is rapidly reduced at the moment when the storage battery pack is loaded after an alternating current power supply disappears, so that the normal power supply related to the load is influenced, even the transformer substation protection device cannot act, the accident is enlarged or primary equipment is burnt, huge economic loss is caused, the power supply reliability is greatly reduced, because the capacity of the battery pack does not play a due role, even the power failure of the whole station can be enlarged due to the common line failure, when the storage battery pack cannot normally supply power, how to guarantee reliable power supply of a direct current system after an alternating current power supply disappears and guarantee that a protection device can act correctly is a problem to be solved urgently.

SUMMERY OF THE UTILITY MODEL

To solve the above problem, the present invention provides a dc power supply system with an abnormal protection mechanism, which in one embodiment comprises: the system comprises a power correction charging module, a super capacitor module, a boosting module and a control module;

the input end of the power correction charging module is connected with an alternating current power supply circuit through an AC/DC converter to supply power to the super capacitor module;

the input end of the super capacitor module is connected with the power correction charging module, the output end of the super capacitor module is connected with the boosting module, and the boosting module is combined to supply power to the primary equipment and the secondary equipment on the direct current side with power supply requirements;

the power correction charging module, the super capacitor module and the boosting module are all in communication connection with the control module, and the control module controls the operation of the modules according to the collected state information.

Preferably, in one embodiment, the power correction charging module includes a rectifying unit, a charging circuit, a power factor correction circuit, and a resonance isolation unit;

the input end of the rectifying unit is connected with the AC/DC converter, and the output end of the rectifying unit is connected with the charging circuit;

the charging circuit adopts a boost circuit topology and comprises a charging inductor (L), a charging switch tube (Q), a charging diode (D), a charging capacitor (C) and an auxiliary load;

the input end of the charging inductor is connected with the output end of the rectifying unit, the charging switch tube is connected with the charging inductor in parallel, the charging diode is connected with the charging inductor in series, and the charging capacitor is further connected with the charging diode; the auxiliary load is connected to two ends of the charging capacitor in parallel;

the input end of the power factor correction circuit is connected with the rectifying unit through the DC/DC converter, and a continuous average current control mode based on the current signal control of the DC/DC converter is adopted;

the resonance isolation unit comprises a resonance circuit and an output circuit which are electrically connected, and a switch in the resonance circuit adopts a zero-voltage soft switch circuit.

In one embodiment, the power factor correction circuit comprises: the circuit comprises a current-voltage sampling circuit, a current loop, a voltage loop, a multiplier and a correction circuit;

the current and voltage sampling circuit adopts a set current sampling element (S) to collect a current sampling value of a charging inductor (L), and is provided with a first voltage dividing resistor (R1) and a second voltage dividing resistor (R2) to perform voltage division sampling on rectified voltage, and is also provided with a third voltage dividing resistor (R4) and a fourth voltage dividing resistor (R5) to perform voltage division sampling on voltage output by the charging circuit;

the correction circuit includes a first comparator (K1), a second comparator (K2), and a third comparator (K3); the reverse input end of the first comparator receives the current sampling value, and the forward input end of the first comparator is connected with the output end of the multiplier; the input data of the multiplier comprises voltage sample values and an output voltage error signal (Ue);

the positive input end of the second comparator is connected with the output end of the first comparator, the negative input end of the second comparator is connected with the sawtooth wave signal, and the output end of the second comparator is connected with the base electrode of a switching tube of the switching circuit;

the positive input end of the third comparator is connected with the standard voltage signal, and the negative input end of the third comparator is connected with the output voltage sampling signal;

the current loop is connected between the negative input end and the output end of the first comparator, so that the current waveform of the input power factor correction circuit is closer to a sine wave;

the voltage loop includes a capacitor (C4) connected between the negative input terminal and the output terminal of the third comparator, which keeps the output voltage constant.

Specifically, in one embodiment, the rectification unit adopts a full-wave rectifier and outputs a sinusoidal half-wave direct-current voltage.

Further, in one embodiment, the current loop includes a first resistor (R7), a first capacitor (C2), and a second capacitor (C3), the first resistor and the first capacitor being connected in series, the second capacitor being connected in parallel across the first resistor and the first capacitor.

In one embodiment, the resonant isolation unit acts as a secondary isolated transforming element that receives primary energy from the power factor correction circuit through transformer isolation.

Specifically, in one embodiment, the resonance isolation unit comprises a point-connected resonance circuit and an output circuit, and a zero-voltage soft switching circuit is adopted as a switch in the resonance circuit;

the resonant circuit comprises a resonant capacitor (Cs) connected with a first switching tube (Q1) and a second switching tube (Q2), and a first resonant inductor (Ls) and a second resonant inductor (Lp) which are sequentially connected with the resonant capacitor in series, wherein the output end of the second resonant inductor is connected with the second switching tube;

the output circuit comprises a transformer, a first filter diode (D1), a second filter diode (D2), an output capacitor (Cout) and an output auxiliary load Rout, the output circuit is electrically connected with the resonance circuit through the transformer (Tr), the first filter diode and the second filter diode are respectively connected with a secondary side of the transformer to form a full-wave rectification circuit, and direct current is provided for the output load through the connected output capacitor; wherein the first filter diode and the second filter diode are fast recovery diodes.

In one embodiment, the zero-voltage soft switching circuit of the resonant isolation unit comprises a zero-voltage resonant soft switch (Sr), an auxiliary inductor (Lr) connected in parallel with the zero-voltage resonant soft switch, and an auxiliary capacitor (Cr) connected in series with the zero-voltage resonant soft switch, and the first switching tube and the second switching tube of the resonant circuit are respectively connected to two terminals of the zero-voltage resonant soft switch.

In one embodiment, the super capacitor module comprises a super capacitor bank and a capacitor equalization circuit;

the capacitance equalization circuit is connected with each super capacitor, and comprises: a plurality of sets of first equalization switches (S1) and second equalization switches (S2) connected to each supercapacitor, each set of first equalization switches and second equalization switches being connected in parallel with a corresponding supercapacitor;

the control module generates control instructions corresponding to the equalization switches according to the collected voltage data of the super capacitors, and the capacitance equalization circuit controls the equalization switches to operate according to the control instructions of the control module, so that the voltages of the super capacitors are kept balanced.

In one embodiment, the boost module adopts a boost circuit, the input end of the boost circuit is connected with the output end of the super capacitor module, and the boost module comprises a first boost capacitor (C10), a boost inductor (L10), a boost switching tube (Q10), a boost diode (D10), a second boost capacitor (C20) and an auxiliary Resistor (RL);

the first boost capacitor filters the input voltage, the input end of the boost inductor is connected with one end of the first boost capacitor, the boost switch tube is connected between the output end of the boost inductor and the other end of the first boost capacitor, and a boost diode and a second boost capacitor are sequentially connected on a branch circuit which is connected with the boost switch tube in parallel;

and the auxiliary resistor is connected to two ends of the second boosting capacitor in parallel.

Compared with the closest prior art, the utility model discloses still have following beneficial effect:

the utility model provides a pair of DC power supply system who possesses unusual protection mechanism, this system is by power correction charge module, super capacitor module, boost module and management and control module constitution, the utility model discloses a power supply system can be with the operation of battery reserve power supply module parallel combination, wherein adopts super capacitor module as middle and energy storage device, even when battery reserve power supply performance trouble can't effectively provide reserve electric energy, meets the circumstances of outage or strong voltage fluctuation, also can timely control protection circuit work, avoids unusual influence to expand on a large scale, endangers the primary equipment of demand side;

in addition, the system adopts the power correction charging module to supply power to the super capacitor module, controls the utilization performance of the super capacitor to be highest, saves the cost and the occupied space of the super capacitor, simultaneously realizes direct current power supply on the demand side by combining the boosting module, improves the utilization rate of energy in the super capacitor as much as possible, and further ensures the normal operation of a protection circuit when abnormity occurs.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, together with the description of embodiments of the invention, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic structural diagram of a dc power supply system with an abnormal protection mechanism according to an embodiment of the present invention;

fig. 2 is a structural topology diagram of a charging circuit in a power correction charging module of a dc power supply system according to an embodiment of the present invention;

fig. 3 is a topology diagram of a power factor correction circuit of a dc power supply system according to an embodiment of the present invention;

fig. 4 is a comparison graph of the average value of the inductive current of the power correction charging module of the dc power supply system and the rectified voltage waveform;

fig. 5 is a topology diagram of the operation principle of the resonance isolation unit of the dc power supply system according to another embodiment of the present invention;

fig. 6 is a topology diagram of a zero-voltage soft switching circuit of a resonant isolation unit of a dc power supply system according to an embodiment of the present invention;

fig. 7 is a structural topology diagram of a voltage equalization circuit in a super capacitor module of a dc power supply system according to another embodiment of the present invention;

fig. 8 is a topology diagram of a boost circuit of a dc power supply system according to an embodiment of the present invention.

In the drawings, like parts are provided with like reference numerals. The figures are not drawn to scale.

Detailed Description

The following will combine the drawings and the embodiments to describe the embodiments of the present invention in detail, thereby the implementer of the present invention can fully understand how to apply the technical means to solve the technical problem, and achieve the realization process of the technical effect and implement the present invention according to the above-mentioned realization process. It should be noted that, as long as no conflict is formed, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are all within the scope of the present invention.

The terms "first," "second," and the like may be used herein to describe various elements, but these elements should not be limited by these terms, which are used merely to distinguish one element from another. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. When an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The direct current power supply system is an important component of a transformer substation, is a power supply of secondary systems such as a relay protection control device, an automation device, a high-voltage circuit breaker switching-on and switching-off mechanism, communication, metering, emergency lighting and the like, and mainly comprises a storage battery pack and a rectifying device, wherein the input end of the storage battery pack is connected with an alternating current power supply end, and the output end of the storage battery pack is connected with a direct current bus or a load. Under the normal operation condition, the direct current power supply system is supplied by station alternating current through the rectifying device, and when sudden alternating current is lost, the station direct current power supply system is supplied with power by the storage battery pack, so that the storage battery pack becomes the only direct current power supply. However, the storage battery pack is used as a backup power supply, the following safety hazards are common, because the maintenance amount of the storage battery pack is huge, a large number of storage battery packs are not maintained in place every year in the existing system, the operation conditions of the storage battery packs in some stations are severe and basically have no capacity, and the operation and inspection personnel cannot monitor and know the conditions in time, under the condition, the voltage of a direct current bus is rapidly reduced at the moment when the storage battery pack is loaded after an alternating current power supply is lost, so that the normal power supply related to the load is influenced, even the transformer substation protection device cannot act, the accident is expanded or one-time equipment is burnt, huge economic loss is caused, the power supply reliability is greatly reduced, for example, at the end of 8 months in 2020, a 110kV transformer substation has a line fault due to thunderstorm, the power utilization cabinet fault of the substation is caused, when the alternating current power supply is switched, a rectifying module loses a working power supply, the storage battery pack supplies power for the total-station protection and automation device, but because the battery running time of the station is too long, the internal resistance of the battery generally and seriously exceeds the standard, the capacity is greatly reduced, the battery is opened at the moment with a direct current load and loses power of a direct current system, the protection device loses the locking of a working power supply and fails to cut off a fault point, a multi-surface switch cabinet is burnt, and the multi-station protection and automation device is tripped out of level, so that a vicious accident of power failure of the total station is caused, and serious adverse effects are caused to the society. The accident is

Because the battery pack has no capacity and does not play a due role, even the total station power failure can be enlarged from a common line fault, when the storage battery pack cannot normally supply power, how to guarantee reliable power supply of a direct-current system after an alternating-current power supply disappears and guarantee that a protection device can correctly act is a problem to be solved urgently.

Specifically, the lead-acid storage battery is the mainstream choice of the direct-current power supply system of the power plant and the transformer substation at present, and accounts for more than 99% of the total loading capacity. In practical applications, however, the lead-acid battery inevitably has the following risk factors that may cause the lead-acid battery not to be normally powered:

(1) the requirement on the operating environment is high:

the lead-acid storage battery generally requires that the operating environment temperature is controlled between 15 ℃ and 30 ℃, and the optimal operating environment temperature is 25 ℃. However, in actual operation, because the aspects of design, operation and maintenance are not in place, the operation temperature of the storage battery cannot be maintained within a specified range, and the capacity and the service life of the storage battery are directly affected. Tests have shown that the battery life is shortened 1/2 for every 10 c increase in temperature when the ambient temperature is above 40 c.

(2) The safety is poor:

in the running process of the lead-acid storage battery, the internal electrolyte of the lead-acid storage battery has overflow risks, so that equipment corrosion and personal injury accidents are easily caused, and when the overflow electrolyte drops onto other batteries or equipment, a direct-current system is easily grounded and short-circuited; the valve-regulated lead-acid battery is sensitive to overcharge, and has the danger of combustion and explosion under the condition of overcharge; in addition, the lead-acid storage battery has hydrogen gas separated out at the end of charging or when overcharged, if ventilation is poor, the hydrogen gas is gathered, so that detonation accidents are easily caused, and an independent storage battery chamber is required to be arranged when the capacity exceeds 300Ah according to regulations.

(3) The service life is short:

the single battery has poor consistency, partial batteries are over-charged (under-charged) for a long time, and the performance is seriously degraded. The storage battery is insufficiently charged, lead sulfate on the polar plate can not be completely dissolved and is accumulated on the polar plate, so that the negative polar plate is sulfated, active substances are reduced, the internal resistance of the storage battery is increased, the capacity is reduced, and the storage battery fails in advance; the ambient temperature rises or overcharge causes the storage battery to lose water, the specific gravity of the electrolyte is increased, the acidity aggravates the corrosion of the positive plate, and the internal open circuit of the storage battery is caused; the cost is low due to blind pressure of part of manufacturing plants, and the thickness of the polar plate and the concentration of the electrolyte do not meet the standard requirements, so that the corrosion of the polar plate is accelerated, and the service life of the battery is further shortened; batteries in different batches cannot be matched and exchanged, individual batteries are degraded, the whole battery pack needs to be replaced, the whole service life is shortened, and great resource waste is caused.

(4) The operation and maintenance workload is large:

according to the national grid company 'national grid DC power supply system equipment overhaul standard', the valve-controlled sealed lead-acid storage battery is inspected at least 1 time per year, and inspection items comprise 4 major items and 12 minor items of terminal voltage, internal resistance, temperature and appearance; the lead-acid storage battery has the advantages that the checking capacity test is required to be carried out regularly due to the fact that checking discharge workload is large, the lead-acid storage battery is determined to be required to carry out the checking capacity test regularly due to the characteristics of the lead-acid storage battery, the charging and discharging multiplying power is low, the test is carried out periodically according to the conventional test method and the requirement of counter measures, the charging and discharging time is long, a large amount of manpower and material resources are consumed, and the on-site over-period detection phenomenon is common.

(5) The condition monitoring is difficult:

in the floating charging state of the storage battery, monitoring the appearance, the environmental temperature and the terminal voltage of the storage battery cannot visually judge the insufficient capacity and other internal quality problems of the storage battery, and the potential hazards of corrosion of a polar lug of the storage battery, virtual connection of a connecting wire and the like are difficult to find by means of small-current discharging and the like; the single group of storage batteries has no redundancy in power supply, and when the station is in AC power loss, high current impact and unexpected low voltage, the phenomena of battery open circuit and short time capacity 'water jump' collapse can occur, and the DC bus voltage loss accident is caused.

(6) The environmental protection pressure is large:

lead-acid batteries contain heavy metal lead and corrosive acid electrolytes, which can cause harm to human bodies, and lead-acid batteries can cause pollution to the natural environment due to improper treatment of waste lead-acid batteries. The power system uses a large amount of lead-acid batteries, the environmental protection pressure is higher and higher, and the social responsibility cannot be ignored. At present, lead-acid batteries adopted by a direct-current power supply system of a transformer substation hardly have a promotion space, and a more reliable scheme is needed to fill the pain point of the years.

The capacitor is an electronic device for storing electric charge, and is widely applied to many electronic devices, but due to the rapid development of the industry technology in the new period, the early circuit structure is gradually replaced by a more complex circuit form, the common capacitor cannot meet the requirement of circuit operation, and the super capacitor is produced as a charge storage device and is generally used as a backup power supply for supplying power to micro current such as a vacuum switch, an instrument, a digital camera, an equipment communication module and the like; solar products and small-sized charging products, but no technology for effectively applying a super capacitor to a power supply system of a power grid to support a power failure protection mechanism has appeared.

Although the advantages of the supercapacitor are many, it is not advantageous in all aspects, and due to the principle of the supercapacitor, it has the following disadvantages: leakage damage, unreasonable installation position of the super capacitor, easy leakage of electrolyte and other problems, and damage to the structural performance of the capacitor. Secondly, the circuit is limited, and the super capacitor is only used by a direct current circuit, because the super capacitor has larger internal resistance compared with an aluminum electrolytic capacitor, the super capacitor is not suitable for the operation requirement of an alternating current circuit. And the price is high, and because the super capacitor is a new generation of high-tech product, the price is relatively high when the super capacitor is just put on the market, and the cost investment of equipment operation is increased. Due to the limitation of manufacturing technology, the defects of installation, debugging and the like exist when the super capacitor is used in China, circuit faults are caused due to blind use of the super capacitor by a plurality of devices, and the performance of the whole device is influenced.

Based on the above current situation, the utility model discloses use and optimize the setting consideration based on super capacitor, provide one kind and can ensure alternating current power supply and break off, can effectively protect direct current generating line and load not receive the direct current power supply system of harm when storage battery abnormal operation, adopt the direct current power supply system who possesses the power-off protection mechanism in this application, even the normal work power supply of direct current load protection device can't be guaranteed to storage battery internal failure, the utilization includes that super capacitor's supplementary power module also can provide the electric quantity that the required electric quantity of suggestion and cut off the fault point for direct current load and protection device, can effectively be minimum with the harm and the influence control of outage.

In addition, it should be noted that although the super capacitor can be regarded as the supplementary guarantee module of direct current system theoretically, the present technology is not perfect, if not according to reasonable structure deployment circuit, can't solve traditional lead acid battery reliability difference completely, intelligent degree is low, the manual work volume is big, the life-span is short, essential safety is not enough scheduling problem, next based on the drawing detailed description the utility model discloses direct current power supply system of embodiment.

Examples

When the super capacitor is not charged, the voltage is zero, and the super capacitor is in a short-circuit state, so that the charging module is required to start working from 0V, the super capacitor can be filled as soon as possible, and the working requirement of the direct current bus is met rapidly. This requires the charging module to output as much current as possible when the output voltage is low. When the voltage of the super capacitor reaches the voltage boosting unit and can work normally, the charging module supplies power to the voltage boosting module and charges the super capacitor, the voltage boosting module is responsible for supplying power to the direct current bus, the technical level of the charging module at present completely meets the charging requirement of the super capacitor, when the charging unit supplies power to the super capacitor module, the voltage boosting unit is in a light-load working state for a long time, so that the efficiency of the voltage boosting unit in light-load working is required to be high, under the condition that the capacity of a direct current system is certain, the higher the efficiency of the charging module is, the smaller the capacity of the super capacitor equipped by the system can be, if the efficiency of the voltage boosting unit is too low, more super capacitors are required to be equipped, the system cost is increased, and the occupied space can be increased. The difficulty is to meet the requirements of impact power during operation and efficiency of long-time light-load operation.

Fig. 1 shows a schematic structural diagram of a dc power supply system with an abnormal protection mechanism according to a first embodiment of the present invention, and referring to fig. 1, the dc power supply system includes: the system comprises a power correction charging module, a super capacitor module, a boosting module and a control module;

A method for improving power Factor in the field is called PFC (Power Factor correction) power Factor correction, a charging module in the embodiment of the scheme adopts a two-stage power conversion charging circuit, a front stage adopts boost topology to correct the power Factor, and a rear stage adopts an LLC high-efficiency isolation converter to control output to charge a super capacitor. The front stage specifically adopts APFC (active Power Factor correction) active Power Factor correction, so that the full-load Power Factor reaches above 0.995, the harmonic current content is controlled below 5%, the pollution to a Power grid is very small, the requirement on a Power supply is low, and a larger Power supply does not need to be provided as long as an alternating current Power supply meets the Power requirement.

Therefore, in one embodiment, the power correction charging module comprises a rectifying unit, a charging circuit, a power factor correction circuit and a resonance isolation unit;

the input end of the rectifying unit is connected with the AC/DC converter, and the output end of the rectifying unit is connected with the charging circuit; the rectifying unit is a full-wave rectifier and outputs sine half-wave direct-current voltage;

the charging circuit adopts a boost circuit topology, and comprises a charging inductor L, a charging switch tube Q, a charging diode D, a charging capacitor C and an auxiliary load, as shown in FIG. 2;

Based on the above structure, the charging circuit of the present system basically belongs to a switching power supply, and is different from the conventional switching power supply in that: the system has no filter capacitor before DC/DC conversion, the voltage is half-wave sine pulsating voltage output by a full-wave rectifier of a filter unit, the sine half-wave sine pulsating direct current voltage, the output current of the DC/DC rectifier and the voltage output by a charging circuit are detected and monitored by a monitoring module in real time, and the control result is that the input power factor of the full-wave rectifier is approximate to 1.

Based on power factor correction strategy, the utility model discloses the product adopts continuous current mode (CCM mode), and direct current control in the CCM mode derives from the current control mode of DC/DC converter.

When the direct current control mode is applied, the input voltage signal is multiplied by the output voltage error signal to be used as a current given signal of the current controller, and the current controller controls the input current to change according to the given signal. The Boost PFC circuit using the average current control technique is described with reference to the accompanying drawings, and a circuit topology is shown in fig. 3;

specifically, as shown in fig. 3, in one embodiment, the power factor correction circuit includes: the circuit comprises a current-voltage sampling circuit, a current loop, a voltage loop, a multiplier and a correction circuit;

the current and voltage sampling circuit adopts the arranged current sampling element S to collect the current sampling value of the charging inductor L, and is provided with a first voltage dividing resistor R1 and a second voltage dividing resistor R2 to perform voltage division sampling on the rectified voltage; the third voltage-dividing resistor R4 and the fourth voltage-dividing resistor R5 are also arranged to divide and sample the voltage output by the charging circuit;

the correction circuit includes a first comparator K1, a second comparator K2, and a third comparator K3; the reverse input end of the first comparator inputs the current sampling value, and the forward input end of the first comparator is connected with the output end of the multiplier Z; the input data of the multiplier comprises voltage sampling values and an output voltage error signal Ue;

the positive input end of the second comparator K2 is connected with the output end of the first comparator K1, the negative input end of the second comparator K2 is connected with a sawtooth wave signal, and the output end of the second comparator K2 is connected with the base electrode of a switching tube of the switching circuit;

the current loop is connected between the negative input end and the output end of the first comparator, and the current waveform of the input power factor correction circuit is closer to a sine wave;

the voltage loop comprises a capacitor C4, which is connected between the negative input terminal and the output terminal of the third comparator, and keeps the output voltage constant.

In one embodiment, the current loop includes a first resistor (R7) connected in series with a first capacitor (C2) and a second capacitor (C3) connected in parallel across the first resistor and the first capacitor.

The average current control of the system adopting the above embodiment has the advantage of a double-loop control technology, the current loop makes the input current waveform closer to a sine wave, the voltage loop makes the boost DC/DC output voltage UO constant, the current sampling element s obtains the current sampling in the charging inductor L, and the voltage sampling element s divides the current by the voltage dividing resistors R1 and R2 to obtain the rectified voltage sampling signal. The K1 positive input signal comes from the multiplier Z as the reference signal of K1, and the K1 negative input signal comes from the inductor current sampling signal. When the inductor current is small, the output of the K1 increases, the duty ratio of the PWM signal after comparison with the sawtooth wave increases, and the on time of the charging switch tube Q is increased and the off time is decreased.

In a Boost PFC circuit, a Q tube is conducted, L stores energy, and a current i passes through an inductor_LWhen the Q tube is cut off, the charging diode D is conducted, the capacitor C is charged, and the current i flowing through the inductor_LIs reduced so that the current i in the inductive circuit is reduced_LTrackable reference signal waveform, i.e. i_LAverage value of I and rectificationThe latter voltage waveforms are nearly in phase, as shown in FIG. 4;

in a Boost PFC circuit at the previous stage, if a PWM signal period is T and Q tube cut-off time is TOH, UO is T/TOH.UI, when UO in the Boost PFC circuit rises, a sampling value of output voltage is compared with a standard voltage Uref, and then K2 output is reduced, so that UZ is reduced; the K1 output is decreased, i.e., TOH is increased and UO is decreased to keep the output voltage stable.

The resonant isolation unit serves as a secondary isolation transformation element which receives primary energy from the power factor correction circuit through transformer isolation. In one embodiment, the resonance isolation unit comprises a resonance circuit and an output circuit which are electrically connected, and the switch in the resonance circuit adopts a zero-voltage soft switch circuit.

The system adopts an LLC high-efficiency isolation conversion mode, adopts full digital control, has the characteristics of high efficiency, smaller volume, lighter weight, higher reliability and the like, realizes isolation power conversion, and has a working principle topological diagram as shown in FIG. 5;

as shown in fig. 5, the resonant circuit includes a resonant capacitor Cs connected to the first switching tube Q1 and the second switching tube Q2, and a first resonant inductor Ls and a second resonant inductor Lp sequentially connected in series with the resonant capacitor, wherein an output end of the second resonant inductor is connected to the second switching tube;

the output circuit comprises a transformer, a first filter diode D1, a second filter diode D2, an output capacitor Cout and an output auxiliary load Rout, the output circuit is electrically connected with the resonance circuit through a transformer Tr, the first filter diode and the second filter diode are respectively connected with a secondary side of the transformer to form a full-wave rectification circuit, and direct current is provided for the output load through the connected output capacitor; wherein the first filter diode and the second filter diode are fast recovery diodes.

In the working process, soft switching control is realized by controlling the on-off time of Q1 and Q2, primary energy is efficiently and accurately transmitted to a secondary, and accurate control of output voltage and power is realized. Specifically, the upper half cycle Q1 is conducted, Q2 is in an off state, the Vin voltage charges Cs through Q1, Ls and Lp, the primary voltage of the transformer is Vin-Vcr, and the transformer outputs energy; when the Q1 is turned off, the sine wave current has not been returned to zero, which can make the Q2 in zero voltage condition, at which time the Q2 is turned on, and the circuit enters the next half cycle operation. In the second half cycle, the stored energy voltage on the Cs forms LC resonant discharge through Q2, Ls and Lp, and the transformer outputs energy to complete the work of one cycle.

In an alternative embodiment, the zero-voltage soft switching circuit applied to the resonant isolation unit includes a zero-voltage resonant soft switch Sr, an auxiliary inductor Lr connected in parallel with Sr, an auxiliary capacitor Cr connected in series with Sr, and a first switching tube and a second switching tube respectively connected to two ends of the soft switch Sr, and the schematic topology of the zero-voltage resonant soft switching circuit is shown in fig. 6.

As shown, the inductor Lr and the capacitor Cr may be basic elements in the topology, or may be auxiliary elements designed specifically for Sr-switch softening. B. The connecting line of the two terminals C can be a direct short circuit of a circuit and can also be a high-frequency equivalent connection.

The resonant switch composed of Lr, Cr and Sr can be regarded as a link in the whole power conversion topology, in the switch transition process, by utilizing the resonant process of Lr and Cr, when the inductor Lr evacuates the stored charge of the capacitor Cr outwards, the voltage of the Sr end drops to zero, Sr is just started to be conducted, zero voltage is started, the Sr end voltage is zero when the Sr is conducted, Sr is suddenly turned off, Lr and Cr can form resonance, the resonant current is charged into the capacitor Cr from top to bottom, the charging rate is determined by the resonant frequency of Lr and Cr, compared with the falling edge time of the current waveform of a switching tube, the rising process of Cr on the voltage is much slower, and the zero voltage turn-off can be regarded as zero voltage when the Sr current drops to zero and is not negligible when the Cr current is not established, obviously, the zero voltage turn-off of Sr is completed under the buffer protection of Cr.

In practical application, the initial current of the charging module for charging the super capacitor is 13.5A, when the output voltage of the charging module reaches 55V, the output current of the charging module is reduced along with the rise of the output voltage, the constant power output of the charging module is controlled to be 750W, when the output voltage of the charging module reaches a set voltage, the module supplies power to a set load, the output voltage is 220-260 Vdc and the output power can be set during constant power output.

The charging and energy storage modes of the conventional super capacitor are two types:

(1) constant current charging

The constant-current charging has the main characteristics of high adaptability and capability of selecting a charging power supply at will. The supercapacitor is charged with a constant current, and the terminal voltage of the supercapacitor is seen to rise along a straight line rule along with time. Due to the fact that the charging current of the super capacitor is wide in selection range, optimization control can be conducted according to different application requirements and the conditions of the super capacitor. For example, for the time-sensitive situation such as the electric bus charging station, the charging mode with large current and short time can be selected: for standby current systems such as UPS, small currents may be used to supplement energy.

The constant current charging is changed into sectional constant current charging, namely, a larger charging current is set at the initial charging stage, and then the set value of the charging current is changed and reduced according to the monitored terminal voltage value in time, and the method is also called a decreasing current charging method.

(2) Float charging

Like electrochemical power sources, supercapacitors self-discharge in the form of leakage current when held at rest, and in particular supercapacitors using organic electrolytes have a somewhat higher self-discharge rate. From the electrical application perspective, it can be considered that the equivalent parallel impedance REP of the super capacitor consumes a part of the electric energy when at rest, and the instantaneous low-power discharge also causes the super capacitor to lose a part of the energy. Therefore, the best way to maintain the backup energy stored in the super capacitor is to continuously float and charge the super capacitor to reduce the backup energy. The volatilization or decomposition speed of the electrolyte of the super capacitor is increased along with the increase of the applied voltage of the super capacitor, and meanwhile, the service life of the super capacitor is also reduced along with the increase of the working voltage, so the voltage monitoring needs to be paid attention to in the floating charging and energy storage process of the super capacitor. In the floating charging process, if the selected floating charging voltage is too low, the self-discharge loss of the super capacitor cannot be compensated, the charging energy storage of the super capacitor is insufficient, and the effective energy storage capacity of the super capacitor cannot be fully utilized. The supercapacitor float voltage must not be too high, otherwise it would increase the energy loss too much or shorten its service life due to severe overcharging beyond the rated voltage of the supercapacitor. Therefore, the selection of the float voltage is important for the supercapacitor to ensure a float charge of high reliability.

In one embodiment, the super capacitor module of the system comprises a super capacitor bank and a capacitor equalization circuit;

the capacitance equalization circuit is connected with each super capacitor, and comprises: a plurality of groups of first equalization switches S1 and second equalization switches S2 connected with each super capacitor, wherein each group of first equalization switches and second equalization switches are connected with the corresponding super capacitor in parallel;

The principle of the voltage equalization circuit of a single capacitor is shown in fig. 7, wherein an electrolytic capacitor Cf is used as a target capacitor, and a control module detects the working voltage of each super capacitor in real time through a voltage detection unit, and compares the capacitor (Cmax) with the highest voltage and the capacitor (Cmin) with the lowest voltage in the current working cycle.

In the next working cycle, the switch S1 is turned on, the switch S2 is turned off, the current I1 flows out, passes through S1 and Cf to form a LOOP LOOP1, and Cmax discharges to Cf; when the Cf voltage approaches the voltage of Cmax, the switch S1 is turned off, the switch S2 is turned on, the current I2 flows out of Cf through S2, Cmin to form a LOOP2, and Cf discharges; when the Cf voltage is close to the voltage of Cmin, the switch S2 is turned off, the switch S1 is turned on, and the working process is repeated, so that the voltage difference between Cmax and Cmin is smaller and smaller, and finally the voltage equalization of the super capacitor is realized.

In practical applications, when the single-capacitor voltage equalization system reaches a steady state, the voltage of Cmax is Umax, the voltage of Cmin is Umin, and the voltage of f varies between U12 and UN. The equalization process can be divided into two steps of charging and discharging:

(1)T₀≤t≤T_onphases

At T ═ T₀At time S1 is on, S2 is off, Cmax discharges to Cf, Cf has initial voltage Uf2, and voltage Uf1(t) at time t. The super capacitor, Cf, and switch in LOOP1 of fig. 3.1 are each replaced by their respective equivalent circuits. The super capacitor may employ a series RC model, where RC is the equivalent series internal resistance. Cf can be equivalent to an electrolytic capacitor with low equivalent series resistance, and the circuit model is composed of an ideal capacitor and an equivalent series internal resistance RD. Since the capacity of Cmax is much larger than that of Cf, Cmax can be equivalent to a voltage source in a very short time.

(2)T_onT is less than or equal to T stage

At T ═ T_onAt time S1 is turned off, S2 is turned on, Cf discharges to Cmin, the initial voltage of Cf is Un, and the voltage at time t is Uf2 (t). In fig. 3.1, the super capacitor, Cf and the switch in the LOOP2 are respectively replaced by their equivalent circuits, and by reducing Cmin and the like to a voltage source in the same way, where T is the switching period of the switching tube, when the charging and discharging time is equal, i.e. T is T/2, the charging and discharging termination voltage of the capacitor Cf is Uf1 and Uf2, respectively, then:

in one embodiment, the boost module of the present system employs a boost circuit, an input end of which is connected to an output end of the super capacitor module, and the boost module includes a first boost capacitor C10, a boost inductor L10, a boost switch tube Q10, a boost diode D10, and a second boost capacitor C20;

the first boosting capacitor C10 filters the input voltage, the input end of the boosting inductor L10 is connected with one end of the first boosting capacitor C10, the boosting switch tube Q10 is connected between the output end of the boosting inductor and the other end of the first boosting capacitor, and a boosting diode D10 and a second boosting capacitor C20 are sequentially connected to a branch circuit which is connected with the boosting switch tube in parallel;

the boost circuit also includes an auxiliary resistor RL connected in parallel across C20.

The boost circuit is a common switching direct current boost circuit, controls inductance to store and release energy through switching on and off of a switching tube, so that output voltage is higher than input voltage, and the circuit topology structure diagram is shown in fig. 8;

in practical application, the working process of the booster circuit can be divided into two parts of charging and discharging, and the control module acquires a signal of the running state of the booster circuit and judges the charging and discharging state of the booster circuit; when the super booster circuit belongs to a charging state, the booster switching tube is controlled to be switched on, and when the booster circuit belongs to a discharging state, the booster switching tube is controlled to be switched off;

when charging, the switching tube is conducted, that is, the switching tube MOS tube is equivalent to a line which directly connects the drain D and the source, that is, the MOS tube is short-circuited, at this time, the input voltage flows through the capacitor C1 for filtering, the inductor L1 and the MOS tube Q1 increase linearly with the continuous charging of the L1, and the inductor stores a certain amount of energy when reaching a certain time; in the process, the diode D1 is reversely biased to be cut off, and the capacitor C2 (the capacitor C2 is charged because the capacitor C2 is charged when the capacitor C2 is discharged last time) supplies energy to the load to maintain the load to work;

when the switch tube is not conducting, at this time, Q1 is equivalent to off, and because the inductor has a back electromotive force, the current of the inductor cannot suddenly change, but slowly and gradually discharges. Since the original electrical circuit is disconnected, the inductor can only discharge through the loop of D1, the auxiliary load RL, and C1, that is, the inductor starts to charge the capacitor C2, and the voltage is supplied to C2 before the capacitor C2 is charged, so that the voltage across the capacitor rises.

The system adopts a DC/DC3KW booster circuit, an output capacitor C2 is generally set to be large enough, so that the output end can keep a continuous current during discharging, and at least a fast recovery diode is generally adopted as a diode.

The boosting module in the embodiment can meet the requirements of wide input range, high boosting multiple, large output power and high light load efficiency. In order to enlarge the utilization rate of the energy stored by the capacitor, the system can boost the output voltage to the voltage range required by the direct current bus when the DC/DC boost module inputs 40V; meanwhile, when the bus voltage is lower than 185V, the DC/DC3kW booster circuit is required to be capable of boosting the output voltage to a voltage range required by the bus, so that the input range of the DC/DC3kW booster circuit is 40-185V, namely the high-end working voltage is nearly 5 times of the low-end working voltage. Meanwhile, the voltage of the capacitor is increased to 220V to supply power to the bus, and the voltage increase multiple is 5.5 times. The actual circuit needs to consider the resistance of the inductance coil, and the larger the resistance of the inductance coil is, the smaller the actual gain of the Boost circuit is, so that to achieve 5.5 times of Boost, the internal resistance on the inductance needs to be reduced by increasing the diameter of the inductance wire, and the Boost multiple is realized to meet the Boost requirement. The problem of large power is solved, a switching tube with larger current needs to be selected, and the withstand voltage of the switching tube is selected according to the output voltage to meet the requirement.

Unlike a battery, a super capacitor converts electric energy into chemical energy through chemical reaction and stores the chemical energy in the battery, and when the super capacitor discharges, the chemical energy is converted into electric energy and the electric energy is discharged, the relative voltage is relatively stable, the super capacitor stores energy in a mode that a capacitor stores a core in the capacitor, and a calculation formula Q of the capacitor for storing the core is CU and an energy formula W of the capacitor for storing the core is CU2, so that the fact that the amount of the energy stored in the capacitor is in a direct proportion relation with the square of the voltage on the capacitor is explained. Therefore, the capacity of the capacitor needs to be determined according to the energy required by the bus and the utilization rate of the energy stored by the capacitor, and the capacity of the super capacitor in the system is large or small. If the utilization rate of the energy stored in the super capacitor is too low, not only the cost is increased to equip a larger super capacitor, but also the floor space is increased, so that enough space is provided for storing the super capacitor, and the utilization rate of the energy stored in the capacitor is very important.

The energy utilization rate of the capacitor storage is calculated according to the energy conservation law, the calculation is carried out according to the fact that the capacitor is charged to 220V, and when the bus voltage is lower than 185V, the direct current equipment stops working.

Calculating according to the discharge of the capacitor to 185V, and deducing the utilization rate of the stored energy of the capacitor by using an energy conservation law:

η＝(CUmax2-CUmin2)÷CUmax2×100％＝(2202-1852)/2202×100％≈29.3％

if a boosting module is added to boost the electric energy stored in the 185V-40V voltage of the capacitor and supply the boosted electric energy to the bus for use, the utilization rate is as follows:

η＝(CUmax2-CUmin2)÷CUmax2×100％＝(2202-402)/2202×100％≈96.7％

according to calculation, on the premise of providing the same energy for the bus, the super capacitor used by the direct current guarantee module provided with the boost and voltage regulation module is about one third of the capacitor not provided with the boost and voltage regulation module.

When the super capacitor module has the module power supply of charging, the module that steps up is in the light load operating condition for a long time, so require the module that steps up efficiency at the light load during operation will be high, under the certain circumstances of direct current system capacity, the efficiency of charging unit is higher, and the super capacitor's that the system was equipped with capacity just can be less, and if the efficiency of the unit that steps up is too low, it is equipped with more super capacitor to require, not only increases the system cost, can increase occupation space moreover, adopts the utility model discloses a direct current power supply system only needs a small amount of super capacitor, and occupation space is little.

The management and control module intelligently monitors the whole charging process of the super capacitor, the running state is sensed and uploaded in real time, when the voltage of the super capacitor reaches the working voltage of the boosting module, the boosting module starts to work, the capacitor voltage is boosted to the voltage required by the direct-current bus, and equipment carried by the direct-current bus can work normally. And when the voltage on the super capacitor rises and exceeds the output voltage of the boosting module, the boosting module automatically quits working, and the charging module supplies power to the direct current bus through the reverse-filling prevention diode while charging the super capacitor. When the charging module reaches the set voltage, the super capacitor is fully charged, and only the direct current bus is supplied with power. At the moment, the super capacitor is in a full-capacity standby state, and the boosting module is also in a standby state. When the direct current system has impact load, the super capacitor provides energy, and after the operation is finished, the charging module fills the super capacitor for standby in time. When the alternating current power failure condition occurs, firstly, the direct current bus at the demand side is directly supplied with power for the bus by the super capacitor, when the voltage of the super capacitor is reduced to the output voltage set by the boosting module, the voltage of the super capacitor is boosted by the boosting module and then supplied with power for the bus, the whole process ensures that the direct current bus voltage does not have a large drop phenomenon, and the follow-up load operation is reliably ensured. The super capacitor can guarantee the stability and reliability of the voltage of the direct current bus when the direct current system is abnormal, the protection device can cut off a fault point as long as the normal power supply of several minutes can be guaranteed, the charging module charges the super capacitor again after the alternating current network system recovers to be normal, and the boosting module automatically quits working to complete a working cycle when the voltage on the super capacitor exceeds the output voltage of the boosting module.

The embodiment of the utility model provides an among the DC power supply system who possesses unusual protection mechanism, each module or cell structure can be according to actual power supply and sample demand independent operation or combination operation to realize corresponding technological effect.

It is to be understood that the disclosed embodiments are not limited to the particular structures, process steps, or materials disclosed herein but are to be extended to equivalents thereof as would be understood by those of ordinary skill in the relevant art. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, appearances of the phrase "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

Although the embodiments of the present invention have been described above, the description is only for the convenience of understanding the present invention, and the present invention is not limited thereto. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A dc power supply system with an abnormal protection mechanism, the system comprising: the system comprises a power correction charging module, a super capacitor module, a boosting module and a control module;

2. The system of claim 1, wherein the power correction charging module comprises a rectifying unit, a charging circuit, a power factor correction circuit, and a resonant isolation unit;

3. The system of claim 2, wherein the power factor correction circuit comprises: the circuit comprises a current-voltage sampling circuit, a current loop, a voltage loop, a multiplier and a correction circuit;

4. The system of claim 2, wherein the rectification unit is a full-wave rectifier and outputs a sinusoidal half-wave DC voltage.

5. The system of claim 3, wherein the current loop comprises a first resistor (R7), a first capacitor (C2), and a second capacitor (C3), the first resistor and the first capacitor being connected in series, the second capacitor being connected in parallel across the first resistor and the first capacitor.

6. The system of claim 2, wherein the resonant isolation unit is a secondary isolation transformation element which receives the primary energy from the power factor correction circuit through transformer isolation, the resonant circuit of the resonant isolation unit comprises a resonant capacitor (Cs) connected to the first switching tube (Q1) and the second switching tube (Q2), and a first resonant inductor (Ls) and a second resonant inductor (Lp) connected in series with the resonant capacitor in turn, and an output terminal of the second resonant inductor is connected to the second switching tube.

7. The system of claim 2, wherein the output circuit of the resonance isolation unit comprises a transformer, a first filter diode (D1), a second filter diode (D2), an output capacitor (Cout) and an output auxiliary load Rout, the output circuit is electrically connected with the resonance circuit through the transformer (Tr), the first filter diode and the second filter diode are respectively connected with a secondary side of the transformer to form a full-wave rectification circuit, and the output capacitor is connected to provide direct current for the output load; wherein the first filter diode and the second filter diode are fast recovery diodes.

8. The system according to claim 2, wherein the zero-voltage soft switching circuit of the resonant isolation unit comprises a zero-voltage resonant soft switch (Sr), an auxiliary inductor (Lr) connected in parallel with the zero-voltage resonant soft switch, and an auxiliary capacitor (Cr) connected in series with the zero-voltage resonant soft switch, and the first switching tube and the second switching tube of the resonant circuit are respectively connected to two terminals of the zero-voltage resonant soft switch.

9. The system of claim 1, wherein the super capacitor module comprises a super capacitor bank and a capacitance equalization circuit;

10. The system of claim 1, wherein the boost module adopts a boost circuit, the input end of which is connected with the output end of the super capacitor module, and the boost module comprises a first boost capacitor (C10), a boost inductor (L10), a boost switch tube (Q10), a boost diode (D10), a second boost capacitor (C20) and an auxiliary Resistor (RL);