FIELD OF INVENTION
This invention relates to DSP controlled Triple conversion online UPS with remote monitoring. This invention is also directed to an improved UPS interfaced with a computer.
PRIOR ART
The use of an uninterruptible power system (UPS) to provide power to a critical load is well known. Known uninterruptible power systems include on-line UPS's and off-line UPS's. On-line UpS's provide conditioned AC power as well as back-up AC power upon interruption of a primary source of AC power. Off-line UPS's typically do not provide conditioning of input AC power, but do provide back-up AC power upon interruption of the primary AC power source. Other on-line UPS's are described in U.S. Pat. No. 5,982,652 and U.S. Pat. No. 5,686,768, both of which are incorporated herein by reference. On-line UPS's of the type described in the referenced patents are available from American Power Conversion Corporation, West Kingston, R.I. under the trade names Symmetra and Silcon. This UPS includes an input circuit breaker/filter, a rectifier, a control switch, a controller, a battery, an inverter, an isolation transformer and a bypass switch. The UPS also includes an input for coupling to an AC power source, and an outlet for coupling to a load.
The UPS operates as follows. The circuit breaker/filter receives input AC power from the AC power source through the input, filters the input AC power and provides filtered AC power to the rectifier. The rectifier rectifies the input voltage. The control switch receives the rectified power and also receives DC power from the battery. The controller determines whether the power available from the rectifier is within predetermined tolerances, and if so, controls the control switch to provide the power from the rectifier to the inverter. If the power from the rectifier is not within the predetermined tolerances, which may occur because of "brown out" or "black out" conditions, or due to power surges, then the controller controls the control switch to provide the DC power from the battery to the inverter.
The inverter of the UPS receives DC power and converts the DC power to AC power and regulates the AC power to predetermined specifications. The inverter provides the regulated AC power to the isolation transformer. The isolation transformer is used to increase or decrease the voltage of the AC power from the inverter and to provide isolation between a load and the UPS. The isolation transformer is typically an optional device, the use of which is typically dependent on UPS output power specifications. Depending on the capacity of the battery and the power requirements of the load, the UPS can provide power to the load during brief power source dropouts or for extended power outages. The bypass switch is used to provide a bypass of UPS circuitry to provide the input power directly to the output. The bypass switch may be controlled by the controller to provide bypass of the UPS circuitry upon a failure condition of the UPS.
To provide further power redundancy, it is known to use a second power source to supply power to a bypass switch of a UPS from a second source of AC power. Systems of this type are often
referred to as dual mains systems. Other prior arts show a dual mains UPS that is similar to the previous UPS except that it includes a second input to couple to a second power supply, and UPS includes a bypass switch that selectively couples the second input directly to the output of the UPS. In dual main systems, typically a utility power source is coupled to the first power input of the system and a backup power source, such as a generator is coupled to the second power input of the system. Upon failure of the utility power source, the power system is able to continue to provide power to a load using the battery mode of operation of the UPS, while the generator is powered on and brought to full output voltage. Once the generator is on line, the power system can continue to provide output power in a bypass mode for ah extended period of time from the generator.
Dual main systems may also be used with both power inputs coupled to the same source of input power, but through separate fuses and/or circuit breakers. For many types of power failures, the power will be lost at both inputs, but situations may exist, such as a blown fuse or circuit breaker, where power is lost at only first input, and the bypass switch can be used to continue to provide output power to a load.
The disadvantage associated with dual mains systems is that in bypass mode, it is not normally possible to charge the batteries of the UPS, which will typically be at least partially drained when input power is being supplied by a source at second input.
The conventional scheme used for AC-DC power conversion employs a diode rectifier-capacitor filter combination at the front end. While this scheme is straightforward and economical, it severely deteriorates the quality of the AC supply by drawing peak currents near the peak of the input AC voltage. This current is rich in harmonics (total harmonic distortion, THD, is very high) and results in poor power factor. There are several major disadvantages associated with having high harmonics injected back into the power grid. Such disadvantages include overheating of the distribution lines, distribution transformers and the neutral line interference with communication and control signals, over-voltages due to resonance conditions and most importantly an ineffective utilization of the voltage-ampere (V-A) rating of the utility.
With regulatory agencies more vigilant about power quality and the appropriate standards, e.g. with IEC-555-2 in place, consistent efforts have been made by engineers to develop new circuits for power factor correction (PFC) and/or THD reduction. In conjunction with the PFC circuits, new control schemes have also been proposed. Such is the popularity of some of these circuits and control schemes that manufacturers have come up with specialized integrated circuits (IC)s (e.g. MC34262, UC3854, etc.) dedicated to these circuits.
The following publications constitute background/prior art to the present invention.
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[22] A. R. Prasad, P. D. Ziogas, S. Manias, "A novel passive waveshaping method for single phase diode rectifiers," IEEE Trans. Ind. Electron., IE-37, pp. 521 530, 1990.
[23] K. Yamashita, "Harmonics fighters pursue choke-coil, on converter power supplies", Nikkei Electron., Asia, pp. 44 47, August 1994.
[24] Jih-Sheng Lai, D. Hurst, T. Key, "Switch mode power supply power factor improvement via harmonic elimination methods," IEEE Appl. Power Electron. Conf, Rec., pp. 415 422, 1991.
[25] A. R. Prasad, P. D. Ziogas, S. Manias, "A Comparative evaluation of SMR converters with and without active input waveshaping," IEEE Trans. Ind. Electron. IE-35(3), pp. 461 468, August, 1988.
[26] N. Mohan, T. M. Undeland, R. J. Ferraro, "Sinusoidal line current rectification with a 100 kHz BN-SIT step up converter," IEEE Power Electron. Spec. Conf, Rec., pp. 92 98, 1984.
[27] B. Andreyeak, C. H. Yearn, J. A. O. Connor, "UC3852 controlled on-time zero current switched power factor correction preregulator," Design Guide (Preliminary), Application note U-132, Unitrode Power Supply Design Seminar Manual, SEM 800, 1991.
[28] P. N. Enjeti, R. Martinez, "A high performance single phase AC to DC rectifier with input power factor correction," IEEE Appl. Power Electron. Conf., Rec., pp. 196 203,1993.
[29] M. S. Dawande, G. K. Dubey, "Bang bang current control with predecided switching frequency for switch mode rectifiers," IEEE Power Electron Drives Syst. Conf., Rec., pp. 538 542, 1995.
[30] C. Zhou, R. B. Ridley, F. C. Lee, "Design and analysis of hysteretic boost power factor correction circuit," IEEE Power Electron. Spec. Conf, Rec., pp. 800 807, 1990.
[31] J. J. Spangler, A. K. Behera, "A comparison between hysteretic and fixed frequency boost converters used for power factor correction," IEEE Appl. Power Electron. Conf, Rec., pp. 281 286, 1993.
[32] W. Tang, F. C. Lee, R. B. Ridley, I. Cohen, "Charge control: Modelling, analysis and design," IEEE Power Electron. Spec. Conf, Rec., pp. 503 511, 1992.
[33] W. Tang, Y. M. Jiang, G. C. Hua, F. C. Lee, I. Cohen, "Power factor correction with flyback converter employing charge control," IEEE Appl. Power Electron. Conf, Rec., pp. 293 298, 1993.
[34] H. Endo, T. Yamashita, T. Sugiura, "A high power factor buck converter," IEEE Power Electron. Spec. Conf, Rec., pp. 1071 1076, 1992.
[35] D. Maksimovic, R. Erickson, "Universal-input, high-power-factor, boost doubler rectifiers," IEEE Appl. Power Electron, Conf, Rec., pp. 459 465, 1995.
[36] Bakari M. M. Mwinyiwiwa, P. M. Birks, Boon-Teck Ooi, "Delta-modulated buck-type PWM converter," IEEE Trans. Ind. Appl. 28, pp. 552 557, 1992.
[37] Boon-Teck Ooi, Bakari M. M. Mwinyiwiwa, X. Wang, G. Joos, "Operating limits of the current-regulated delta-modulated current-source PWM rectifier," IEEE Trans. Ind. Appl., 38, pp. 268274, 1991.
[38] P. C. Todd UC 3854, "Controlled power factor correction circuit design," Unitrode-Product Applications Handbook, Lexington, Mass., 1993 94.
[39] Micro Linear Data Book, 1993
[40] R. Oruganti and M. Palaniapan, "Inductor voltage controlled variable power factor buck-type AC-DC converter," Proceedings of Power Electronics Specialists Conference (PESC), pp. 230237,1996.
[4.1] R. Oruganti and Ramesh Srinivasan, "Single phase power factor correction—A review," Sadhana, vol. 22, part 6, pp. 753 780, 1997.
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The advantages of a high power factor and low harmonic distortion are well known. A major advantage is an optimum utilization of power coming out of the utility [1, 16 18]. The past two decades have witnessed a tremendous research effort related to power factor correction in switching power supplies [1, 49]. This could be attributed to the growing awareness about power quality and the seriousness with which the concerned agencies all over the world have started enforcing power quality standards.
The major issues [2 4] concerning power factor correction circuits are the size and the cost of the system, complexity of the circuit topology (e.g. single stage, dual stage, etc.) and its control (e.g. duty cycle control or variable frequency control or a combination of the two), output voltage regulation and its ripple content and the efficiency of the converter (single stage or multiple stage). In earlier days, the trend was to use a boost topology and to modulate its duty cycle, so as to present a resistive load to the line voltage. But any such scheme needs a second stage for isolation and load voltage control. A simple scheme based on a flyback converter operating in a discontinuous current mode (DCM) with constant duty cycle is reported by Erickson et al [5], with isolation incorporated in the first stage. A new power factor correction scheme for a single-phase buck-boost converter is proposed by Prasad et al [6]. Some of the single stage configurations proposed are the isolated boost topology proposed by Yang et al [7], a fast-response topology utilizing the inherent characteristics of resonant boost stage by Kheraluwala et al [8] and the dual switch forward topology proposed by Daniele et al [9]. But these approaches all utilize at least two switches.
Redl et al [4] proposed a new family of power factor corrector circuits (S.sup.2IP.sup.2), which overcame most of the drawbacks of then-existing configurations. Merged configurations of derived boost and buck configurations have also been used for power factor correction (PFC) [10, 11]. Other authors reported on related aspects including reduction of high-voltage stress on primary side devices [12] and electromagnetic interference (EMI) in PFC circuits [13, 14].
This initial overview is followed by presentation of the underlying ideas and classification of the various PFC techniques. More literature review is taken up subsequently.
PFC Technique Attributes:
A good PFC technique should provide the following features:
(a) Harmonic free (sinusoidal) input line current with near unity power factor over a wide load
variation
(b) Good line and load regulation—with fast output dynamics
(c) Small size, low weight, low part count, economy
(d) High power conversion efficiency
(e) Low EMI
In addition to the above, the following may also be desirable depending on the specific application:
(a)Galvanic isolation between input and output.
(b)Universal input AC voltage range (typically 85V to 270V root mean squared (RMS).)
(c)Low output ripple
(d)Wide range of output voltage, from very low DC output (e.g. 12V, 24V, etc.) to high voltage (e.g. 800V)
(e)Good hold-up time if required by the application (Hold-up time is a measure of how long a supply will hold output voltages to within specifications after input power has been lost. For example, a supply with sufficient hold-up time can keep providing power to the load during short power outages.)
Classification of PFC Techniques [41]:
The PFC techniques may be classified into the following categories:
(a) Passive PFC (PPFC)
(b) Active PFC (APFC)
(c) Combination of categories (a) and (b) (PPFC+APFC)
Passive Power Factor Correction (PPFC)
PPFC's make use of inductive filters and resonant filters (combination of L and C) [42, 43]. These techniques do not make use of any additional active devices/circuitry for power factor improvement. Hence, these solutions are simple, reliable and cost-effective at low power levels. But the existing schemes may suffer from the following disadvantages:
(a) These techniques attempt to bring down the harmonic levels to within the limits set by
the standards. They do not attempt to improve it beyond what is required by the
standards. Thus they still do not facilitate an effective V-A utilization.
(b) PPFC does not allow wide input AC voltage variation (e.g. from 85V to 270V). Because
PPFC uses only passive components, it cannot maintain output regulation when the input
fluctuates over a wide range.
(c) To accommodate a wide range of voltage variation one must use active switches and duty
cycle control. For a duty cycle controlled system, for example, a duty cycle ratio range of
0.1 to 1.0 is normal. To allow a wider variation, this range could be widened to 0.01 to 1.
However this will require very high tr and tf times of the switching devices.
(d) At higher power levels the reactive elements of a PPFC tend to be large and bulky and
are no longer cost effective.
(e) At higher power levels, the power factor does not remain within the specified limits over
a wide variation of power levels.
Active Power Factor Correction (APFC)
In contrast to the PPFC techniques, the APFC techniques [6, 26 37, 40] make use of additional devices/control circuitry to improve the power factor and harmonic profile. Therefore, these are expensive techniques as compared to PPFCs. Nevertheless, their overall performance is far superior. The conventional APFCs are, in general, single-stage configurations based on buck, boost, flyback, forward or modified topology, employing one or more switches. The boost and flyback topologies are operated in continuous current mode (CCM) or discontinuous current mode DCM [7, 27 and 33]. It is to be noted that:
(a) Flyback configuration—Control chips are available to implement this kind of configuration. The major disadvantage is high peak currents.
(b) Forward mode—with CCM, the transformer has to operate at the principal frequency (50 Hz, 60 Hz, 400 Hz or other commonly used AC frequencies), thereby increasing the size of the transformer. Thus, DCM operation commends itself by permitting the use of smaller transformers. But it has the disadvantage of higher peak currents.
In APFCs, the input line current is controlled by various techniques such as peak current mode control, average current mode control [12, 26], charge control [17, 18, 32, 33], hysteresis current mode control [15, 16, 30, 31], sinusoidal pulse width modulation (PWM) [14, 28], delta modulation control [21, 22, 36, 37], inductor voltage control [23, 40], etc. In fact many of these control schemes are available as ICs.
APFC could be both current source type (usually buck type) [36, 37] or voltage source type [1, 2, 26]. The voltage source type, which is more popular, may use buck, boost, buck-boost, cuk or derived topology. The following points must be noted regarding these configurations:
(a) A boost configuration, operating in CCM, is suitable for medium to high power level
applications because the boost inductor results in low input supply ripple and hence the filter
requirements are reduced. But this configuration suffers from the disadvantages of high
reverse recovery loss, charge pumping loss, poor EMI performance and to some extent even
cusp distortion near the zero crossings of the input current. Some of these problems may be
alleviated using soft-switching techniques and resonant power conversion techniques.
(b) The problem of reverse recovery of output diode may be eliminated by operating the
boost configuration at the CCM-DCM boundary.
(c) A boost converter operating in DCM does not give a sinusoidal input current unless the
duty cycle of the switching device is varied continuously. Also the peak current stresses on
the devices are remarkable.
(d) The use of flyback (buck-boost) topology can be attractive at lower power levels. It offers
several advantages. For example, absence of the start-up in-rush current problem, easy
implementation of overload protection, the output voltage may be greater or less than the
peak input voltage and possibility of galvanic isolation. Both CCM and DCM modes of
operation are possible, but they result in more noise. The diode reverse recovery problem is
eliminated when operating this topology in the DCM mode.
The existing APFC schemes suffer from atleast one of the following disadvantages:
(a) All the drawbacks of DCM operation.
(b) In many cases the voltage across the bulk energy storage capacitor is uncontrollable and
can reach high values, but at the same time a higher rated capacitor will result in increased
cost and greater power loss due to larger ESR values.
(c) Variation of the frequency in many cases over a wide range (typically 8 times), making
the EMI filter design difficult.
(d) Increased stress on devices.
(e) Low Efficiency of power conversion.
(f) Complex control.
(g) Large filter capacitor to filter second harmonic components,
(h) Slow output dynamics.
Some of the drawbacks mentioned above may be overcome by using modified configurations such as a cascaded configuration [1] comprising two stages with independent control. The first stage corrects the power factor while the second stage provides tight regulation of output voltage against fast and dynamic load. The disadvantage with this scheme is lower efficiency because of two stages. This disadvantage is overcome to some extent by merging the two stages of a cascade configuration into one power stage [44, 45]. This increases the efficiency but the control becomes complex. Many power factor corrected circuits belong to this category. PPFC+APFC: A combination of APFC and PPFC can result in improved efficiency, reduced size and cost [41, 46]. An example of this scheme is where the active power factor correction circuit operates only during some portion of the input AC waveform, while in the remaining portion, a passive network (PPFC), connected in parallel with the APFC circuit, takes over.
Some of the available online UPS do not have monitoring & controlling software interface. The problem faced by using these online UPSs is that when the battery goes low it shuts down the system connected to it abruptly. This results in the loss of data & system failure.
Some of the UPSs which claim to have monitoring & controlling software are associated with following drawbacks-
(a) Existing monitoring & controlling software interface is not real time. They do not provide
instantaneous values of the various parameters of the system and cannot do power audit.
The product up-gradation is also not possible by these softwares.
(b) In the systems where remote monitoring and controlling is possible, an additional card or
hardware (SNMP and other like that) is required to be connected to the UPS system. This
increases the hardware as well as cost of the system.
Some of the UPSs described in U. S. patent application 20060044846, U. S. patent No. 6906933, U. S. patent No. 6661678 and U. S. patent No. 7,157,886 provide power factor corrected UPSs but these or other existing_systems may suffer from atleast one of the following drawbacks:
a) High size, weight and volume of the system.
b) High cost of the system.
c) Variation of input power factor with respect to load and mains.
d) Complex control strategy.
e) Output voltage regulation within the specified range is not possible.
f) High output ripple content.
g) Great peak current stress on the devices and the transformer,
h) Low efficiency of the converter.
i) Load sharing in case of availability of the mains,
j) Charger with ripples and affected power factor,
k) Web monitoring with additional hardware like SNMP.
1) Low load withstanding capacity of the UPS.
OBJECTS OF THE INVENTION
The primary object of the present invention is to propose DSP controlled Triple conversion online UPS with remote monitoring which overcomes disadvantages associated with the prior arts.
Another object of the present invention is to propose DSP controlled Triple conversion online UPS with remote monitoring which is cost effective.
Further object of the present invention is to propose DSP controlled Triple conversion online UPS with remote monitoring which provides high availability power solutions and high load with stand capacity.
Still further object of the present invention is to propose DSP controlled Triple conversion online UPS with remote monitoring with local and remote monitoring and controlling through web and mobile.
SUMMARY OF THE INVENTION;
It uses a novel control scheme based on duty cycle control in conjunction with fixed operating frequencies. A continuously varying operating frequency is not required, reducing the complexity of the control circuit. It results in reduced peak current stress on the circuit components leading to higher circuit reliability. The cost is substantially lower than prior art and operates with high power factor and a well-regulated DC output voltage. This power factor correction circuit apparatus and method is especially suited for 'boost' applications where high DC output voltages (e.g. 380-400V) are needed. One particular embodiment of the invention is in the form of a fully self-contained power converter module. The proposed configuration can be further integrated to reduce system size and will be of especial interest to industries associated with battery charging and uninterruptible power supply (UPS) systems.
Present invention also provides real time management using internet for online uninterruptible power supply connected to computer. The same Digital Signal Processor (DSP) is used to control the entire online UPS communicating with the computer based software to transfer the real time parameters to the computer. This is through the dedicated communication protocol that is implemented inside the DSP and also in the monitoring software. The DSP technology provides faster and precise control of UPS system for effective and safe mechanism. Through the DSP the product up-gradation is also possible as the commands are directly sent to the DSP. This web based facility is without any additional hardware thus reducing the hardware and also the cost of the system. The inverter control section is connected to the computer via any serial port communication cable. The UPS installed anywhere in the world can be centrally monitored and controlled by the user. The present invention also provides facility to monitor & control the UPS via mobile.
Embodiments of the present invention provide cost-effective and high availability power solutions. One embodiment of the present invention is illustrated to FIG. 1, which shows a, functional block diagram of the UPS 100. The UPS 100 includes an AC power input 101, line filter 102, rectifier section 103, power factor correction (PFC) circuit having three separate section (i) input power interface card 104 (ii) PFC choke 105 (iii) PFC & booster power module 106 having PFC & booster controller 107, SMPS (Switched Mode Power Supply) battery charger 108, a battery bank 109, booster choke 110, an inverter 111, IGBT (Insulated Gate Bipolar Transistor) driver 112, inverter controller 113, a power supply unit (PSU) 114, an isolation transformer 115, a DC bus 116 and a bypass circuit having a bypass switch 117. The UPS 100 also includes a power output 118.
Embodiments of the present invention provide improved power systems. In one aspect an uninterruptible power supply for providing power to a load is provided. The uninterruptible power supply includes an input to receive input power, an output to provide output power, an input power circuit coupled to the input and having a DC output that provides DC power, a backup power source coupled to the input power circuit, an output power circuit coupled to the DC output of the input power circuit and to the output of the uninterruptible power supply to provide the output power, and a capacitor discharge circuit coupled to the first end of the capacitor and the second end of the capacitor and configured in a first mode of operation to discharge a voltage across the capacitor, such that an average discharge current through the discharge circuit is
inversely proportional to a voltage across the capacitor.
Another aspect of the invention is directed to an uninterruptible power supply for providing power to a load. The uninterruptible power supply includes a first input to receive input power from an input power source, an output to provide output power, a bypass input coupled to the first input to receive bypass power, wherein the bypass output is selectively coupled to the output to provide output power, an input power circuit coupled to the first input and having a DC output that provides DC power having a first DC voltage level, a back-up power source coupled to the input power circuit to provide DC power at the DC output in a back-up mode of operation, and an inverter circuit coupled to the DC output of the input power circuit and to the output to provide the output power derived from at least one of the input power source and the back-up power source.
The uninterruptible power supply may include means for charging the back-up power source in the mains mode of operation, and may further include a power supply coupled to the input of the inverter circuit to receive DC power and to provide DC power to components of the uninterruptible power supply. The back-up power source may include at least one battery. The power supply may further include a power supply unit receiving power through the input power interface card and further provides power to the PFC, booster control and inverter control sections. It includes DC filter section with fuse, sensing and control circuit and output power supply units.
The uninterruptible power supply may include a SMPS battery charger coupled to the output of the PFC circuit to receive DC power and provide power to charge the back-up power source in the mains mode of operation, and may further include a power supply coupled to the input of the inverter circuit to receive DC power and to provide DC power to components of the uninterruptible power supply. The back-up power source may include at least one battery. The first input and the bypass input may be configured to be coupled to a common source of power. The uninterruptible power supply may include a bypass switch coupled between the bypass input and the output of the inverter circuit and controlled to operate in a closed position in the bypass mode of operation.
Another aspect of the invention is directed to an uninterruptible power supply for providing power to a load. The uninterruptible power supply includes an input to receive input power, an output to provide output power, a backup power device that provides backup power, an input power interface card coupled to the output of the rectifier and input of the PFC choke, backup power device is connected to the input power interface card through the SMPS charger, Booster choke, PFC choke connected to the input interface card giving output to the PFC booster power module. The output of the PFC booster power module gives supply to SMPS charger to charge the backup power device. The PFC booster power module further includes a PFC & booster controller. The output of PFC & booster power module is given to the input of the inverter power module. The inverter power module is driven by IGBT driver which is controlled by the inverter control section using DSP technology. The inverter power module provides the regulated AC output of the uninterruptible power supply. The uninterruptible power supply further includes an
isolation transformer at the end of the inverter power module. It separates out the input neutral and the output neutral so that any disturbance in input does not affect the output. Further any output is not affected by any fault in input. The transformer also blocks the noise in neutral and gives a clear output.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS ;
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawing and wherein:
FIG. 1 shows a functional block diagram of a UPS system in accordance with one embodiment
of the invention;
FIG. 2 shows the circuit diagram of line filter;
FIG. 3 shows the circuit diagram of bridge rectifier;
FIG. 4 shows the circuit diagram of input power interface card;
FIG. 5 shows the diagram of PFC choke;
FIG. 6 shows the circuit diagram of PFC & booster power module;
FIG. 7 shows the circuit diagram of PFC & booster controller;
FIG. 8 shows the circuit diagram of SMPS charger;
FIG. 9 shows the circuit diagram of inverter power module IGBT;
FIG. 10 shows the circuit diagram of IGBT driver;
FIG. 11 shows the circuit diagram of inverter controller;
FIG. 12 shows the circuit diagram of power supply unit;
FIG. 13 shows the circuit diagram of output transformer;
FIG. 14 shows a pictorial diagram of power management system controlled by web monitoring
software using computer system;
FIG. 15 shows a pictorial diagram of power management system controlled by web monitoring
software using mobile;
FIG. 16 shows the flow of the software program pertaining to the operation of the invention for
monitoring purpose of the system;
FIG. 17 shows the flow of the software program pertaining to the operation of the invention for
controlling the various parameters of the system;
DETAILED DESCRIPTION OF THE INVENTION
This invention provides a UPS as shown in fig. 1 comprising of: an AC power input 101, line filter 102, rectifier section 103, power factor correction (PFC) circuit having three separate section (i) input power interface card 104 (ii) PFC choke 105 (iii) PFC & booster power module 106 having PFC & booster controller 107, SMPS battery charger 108, a battery bank 109, booster choke 110, an inverter 111, IGBT driver 112, inverter controller 113, a power supply unit (PSU) 114, an isolation transformer 115, a DC bus 116 and a bypass circuit having a bypass switch 117. The UPS also includes a power output 118.
In a normal mode of operation of the UPS, AC power at the power input is passed through line filter 102 and rectified through the rectifier 103. Power factor is corrected through the input power interface card 104, PFC choke 105 and PFC & booster power module 106. PFC & booster power module 106 is controlled by PFC & booster controller 107 to provide DC power to the DC bus 116.
The filter section 102 (fig. 2) filters the AC input by reducing the ripples and provides the output to the bridge rectifier section 103. The bridge rectifier 103 (fig.3) comprises of atleast four diodes connected to form a bridge. The ac input voltage is applied to the diagonally opposite ends of the bridge.
The rectified AC then passes through the input power interface card 104 (fig.4). The input power interface card 104 provides a medium for connection and lowers the voltage distortion in the circuit. It includes capacitors to filter the DC and shunt resistances to measure current by the voltage drop those current create across the resistance. The input power interface card 104 provides power supply for the different control cards and drivers. The output of input power interface card is sent to PFC choke 105 (fig.5). It is also useful for the prevention of electromagnetic interference (EMI) and radio frequency interference (RFI) from power supply lines and for prevention of malfunctioning of electronic equipment.
The output of PFC choke 105 is boosted and corrected in the PFC & booster power module 106 (fig.6). The PFC & booster power module 106 is controlled by PFC & booster control card 107. The PFC & booster power module 106 consists of DC bus filter section, charging and passive discharge circuits, switching circuits using IGBTs and diodes for high voltage and outstanding efficiency. The capacitors get discharged through the inverter. The capacitor discharge circuit may be configured in the first mode of operation to control the discharge current, such that the discharge current has a waveform containing a series of pulses with a duty cycle of the pulses being inversely proportional to the voltage across the capacitor. The output of PFC & booster power module is provided to SMPS battery charger 108 to charge the battery bank 109 and inverter power module IGBT 111.
In typical UPSs, to meet the safety requirements, either a passive or an active discharge circuit is used. Typical passive circuits use resistors as discharging devices in parallel with the capacitor to be discharged. The use of resistors is desirable as these resistors draw constant power at normal operating conditions. Passive discharge circuits have an advantage over active discharge circuits as they are reliable and reduce the complexity of the circuit.
The discharge control circuit is implemented using a passive discharge circuit that are more reliable than typical active discharge circuits and the power draw of the discharge device remains proportional to the voltage. The use of a continuously passive circuit in embodiments of the invention allows the discharge circuit to operate without the need for external control circuits that activate the discharge circuit when power to the UPS is removed.
PFC & booster control card 107 (fig.7) that controls the PFC & booster power module 106 is comprising of two major sections (i) PFC control circuit and (ii) Booster control circuit. Both the circuits include sensing and controlling circuits and drivers. Power supply circuit 114 (fig. 12) supplies power to sensing and controlling circuits. 1C controls the voltage and current. PFC & booster controller 107 controls the PFC booster power module 106 to maintain the voltage on the DC bus at a desired value to provide a DC voltage to the SMPS battery charger 108 (fig. 8). The Power supply unit 114 receives power through the input power interface card 104 and provides power to the PFC booster controller 107 and inverter controller 113 sections. It includes DC filter section with fuse, sensing and control circuit, and output power supply units. Sensing and controlling circuit senses the voltage and controls the output power supply for different drivers and control cards.
As shown in the prior art, when battery is boosted by PFC circuit, there is always some current flowing through the battery to the load and the load sharing is involved. . If mains voltage is low (say 150V) then the rectifier output would be the multiple of mains (V* 0.9). In that case if UPS is running at full load then it takes some currentjhrough the battery that causes the load sharing by using battery. In the present invention the battery is coupled between the SMPS battery charger 108 and input power interface card 104 as shown in fig.l. The output of the battery bank 109 is provided to the input power interface card 104. Then the DC output goes in PFC & booster power module 106 through the booster choke 105. Thus there is no load sharing because of the booster. It also increases battery backup time and reliability of the batteries. The separate booster gives very good transient response and sends no disturbance in the inverter output waveform when UPS switches from mains to battery and vice versa. Single inductor has unlimited power transfer capability. By using this, UPSs with different ratings can be made (for eg, 1KVA, 2KVA, 10KVA, 20KVA and above that).
In the embodiment shown in FIG. 1 a battery bank 109 is used. However, in different embodiments, the battery 109 may be implemented using a combination of batteries coupled in parallel and/or in series to provide the voltage and capacity necessary for a given implementation. The battery bank in the present invention consists of a number of batteries connected in series. For safety purpose MCB is provided at the positive end of the battery. When there is any fault in the batteries or input circuit, the MCB trips and protects the system. The system gives alarm on low battery and only a maximum current is drawn by the battery so the heating does not exist in the battery module.
The battery bank is charged using a Switch mode power supply (SMPS) battery charger circuit 108. Switch mode power supply (SMPS) based chargers offer improved performance compared to the SCR and the transistor controlled chargers. These chargers offer high efficiency power conversion due to high frequency operation. The high frequency power conversion stage results in significant size reduction for the energy storage elements (transformers, inductors, and capacitors). In addition, these chargers have fast dynamic response. The SMPS battery charger 108 (fig.8) comprising of switching and controlling circuits using ICs, output filter section and
power supply unit to provide power to the switching circuit. A central analog/digital controller is normally employed to regulate the charger voltage/current and to implement the desired charging algorithm. In order to implement constant-voltage and constant-current charging methods, the SMPS charger senses current from the shunt and the current is then limited and controlled by the A/D controller. DC choke smoothes the output charging current. The primary winding current of the transformer is normally sensed and regulated by the control circuitry to achieve the desired level of output current and to implement the constant-current intervals of the charging algorithm. An output capacitor is normally used to filter out any remaining voltage ripple in the filter inductor and thus supplies a pure DC current to the battery. The voltage across the capacitor, which is same as the battery voltage, is normally sensed and regulated by the control circuitry to achieve the desired level of output voltage and implement the constant-voltage intervals of the charging algorithm. The output of filter section is provided to the positive and negative end of the battery bank 109. This feature provides very low ripple charging with no disturbance in input power factor and charging current would be independent of input and output voltage. SMPS does fast control and increases battery life. It also provides constant current thus lowering the heating of batteries. The other key features of SMPS charger are high efficiency, over-volt and load protection, over charge protection, battery temperature compensation and very high reliability.
Inverter module IGBT 111 (fig.9) includes atleast four IGBTs creating H-bridge and capacitors. This type of circuit provides enhanced inrush current withstand capability. Module can double the modulation frequency of the inverter, reduce the switching loss and improve the system efficiency with minimum noise, leading to improvement in performance of system and reduction in cost. The inverter module IGBTs 111 receive the DC power and provide regulated AC power at the power output 118. Control of the circuit is achieved by controlling the IGBTs with pulse width modulation (PWM) through the IGBT driver 112. A controller is being used to generate the required PWM signals.
The PFC & booster controller 107 and inverter controller 113 are used to provide monitoring and control of components of the UPS 100. Inverter controller 113 (fig. 11) is connected to the inverter power module 111 through IGBT driver 112. The inverter controller 113 includes DSP circuit, LCD driving circuit, circuit to convert 12V DC to 5V DC, sensing circuit, a multiplier and a pulse width modulator (PWM). Resistances R9, R31, R42, and R25 can change their values (say 390K for 180V & 820K for 360V) to maintain the output voltage. The inverter controller 113 monitors the input current and voltage of the inverter power module 111. The functions provided by inverter controller! 13 may be implemented using control algorithms in it to operate the inverter power module 111. However, it may also be coupled to numerous sensing devices to monitor operational parameters of the UPS 100. This card provides pulse width modulated input for IGBT driver using four NAND gates Ul 1 A, Ul IB, Ul 1C and UlID. DSP provides protection from short-circuit and overload. DSP card provides RS232/ RJ45/ USB port connection for monitoring and control of the various parameters of the UPS locally and remotely.
IGBT driver card 112 (fig. 10) provides protection & increases current capability of PWM signals. The IGBT driver card 112 receives input signals from inverter control circuit (DSP) 113and provides output drive signals to Inverter module 111. The two complementary PWM signals generated by the DSP cannot be high simultaneously thus this is controlled by the logic gates. IGBT driver card provides isolation between DSP side and IGBT side with the help of optocouplers. If there is any short circuit or voltage drop in the IGBT side and VCE becomes greater than the specified value then the driver takes protection by isolating the DSP side and IGBT side. Since DSP does not have the sufficient current to drive the inverter, IGBT driver card 112 increases the current capability of DSP.
The UPS 100 utilizes voltage control to control operation of the inverter power module 111. The inverter controller 113 senses the voltage and the PWM modulator provides control signals to the inverter power module 111 to control voltage. Voltage is controlled by increasing or decreasing the PWM width as the output voltage decreases or increases.
The current drawn through the rectifier is based on the voltage level of the DC bus, and the phase of the current drawn by the inverter is in phase with the input voltage so that unity power factor is obtained. The voltage of the DC bus 116 can be maintained at a constant level. The novel feature of the present invention is that high power factor (>0.98) in all the conditions is obtained such as with load (25% to 100%) when charger is ON and shows a very low variation in power factor (0.95-0.99) over the entire input range (150V-270V). This feature provides really the advantage of power factor corrections at any load and input mains voltage. Technically this feature is a result of precise design of choke including material selection for choke and gain setting of controller.
The DSP having A/D converter is a 16 bit A/D converter. However, other types of A/D converters, data formats, and ranges may be used as the present invention is not limited to a particular type of A/D converter, a particular format, or a particular range in values. DSP controls all the parameters of UPS and supplies to remote port through which the user can check the status of the UPS and also monitor & control the various parameters remotely.
As understood by those skilled in the art, embodiments of the invention may be implemented using other circuits with other valued components. In addition the values of components provided may be changed to adapt the discharge circuit to accommodate other DC bus voltages.
The inverter power module 111 provides the regulated AC power to the isolation transformer 115 as shown in fig 1. The isolation transformer 115 (fig. 13) is used to increase or decrease the voltage of the AC power from the inverter power module 111 and to provide isolation between a load and the UPS. The isolation transformer 115 is typically an optional device, the use of which is typically dependent on UPS output power specifications. The isolation transformer 115
separates the input neutral & output neutral thus any disturbances or fault in input does not affect the output. It also blocks the noise in neutral and provides galvanic isolation.
The present invention provides high load withstand capacity. It provides 150% load for 10 sec, 200% load for 2 sec and 300% load for 1 sec. Technically this feature comes from precise and tremendous control of DSP. This feature has advantage that the system is best suited for SMPS load because SMPS load draws a lot of current in the beginning. The load may be in the form of pulses and the power gets dissipated in the load itself.
The present invention also provides real time web based remote monitoring as well as multiple user local monitoring for online uninterruptible power supply with the help of Power Management Software using internet as shown in the fig 14 & 15.
Power Management Software includes:
1. Web based monitoring Application.
2. Local Monitoring Application.
With the help of web based monitoring software, the UPS installed anywhere in the world can be centrally monitored and controlled by the user. It supports all operating systems such as Windows version & various Linux, Solaris versions. A licensed copy of the software is installed and run on the computer connected to the power system via any communication cable (say RS-232/ USB port/ RJ-45) through which it starts receiving data. The unique and fully validated software solution allows various parameters of the systems to check and the system can be upgraded, including load and status of each system. The novel feature of the software is that it does not require any additional hardware like SNMP for web monitoring. Even local monitoring is carried out by using TCP/ IP. Use of computer instead of SNMP provides two way communication and product up-gradation which was not possible by using SNMP hardware as seen in the existing monitoring software. The Power Management Software not only controls the start/shutdown of the UPS but also provides control for various parameters in UPS and system up-gradation. The software is very useful for unmanned locations where power backup systems are installed and where their assured availability is essential and mission is critical. Some of the examples are ATMs, Telecom towers; Satellite based systems, online process control equipments, fully networked chain of retail stores, chain of multiplexes, their supply chain systems. Such inherent flexibility lends itself for condition based operational utilization of power backup systems thus adding considerable value and enhancing the maintainability and assured availability of systems.
Local power monitoring software requires a serial connection between a computer & the system via serial port communication cable. Inverter control section connected to the computer via any communication cable (say RS-232/ USB port/ RJ-45) is shown in fig 14 & 15.
The web monitoring software facilitates checking of various parameters in the form of digital and graphical representation. Data logging of these parameters can be ensured at defined time intervals say every 10 or 15 seconds. The flow chart in fig 16 & 17 presents the functioning of the software for monitoring and controlling the system.
Chief components of the Power Management Software
The Power Management Software comprises of the following two components
(A) Local Server application
(B) Local Client Application
(A) Local Server application performs communication with the UPS, its shutdown as well as that of local clients, emailing and broadcasting of UPS events
Interpreting Main Panel
The main panel display provides node information and information on the status of the power, UPS battery system, system operations, and communications. The display automatically detects the configuration of the UPS and adjusts itself accordingly.
The main panel is a graphical representation of the operational status of the system. Input and output voltage, input and output frequencies are shown with the help of analog meters. Battery voltage and Load % along with output current, output power and UPS capacity are indicated with the help of bar graphs.
It provides detailed information regarding the present power situation and controls features such as orderly system shutdown and configuring alerts. It also provides system shutdown time, review of the power event and battery management logs and handling other tasks.
Following are the utilities provided by the software and local server can configure the system accordingly
1. Data view
Data view uses bar graphs and text to show the power situation. The display is divided into sections as follows:
Output
Output information shows the actual output load on the UPS. The output section includes the
following:
• Status: Condition of the UPS battery
• % Load: Percentage of the UPS's calculated full load in use including overload
conditions
• Volts: Output voltage for the load including over voltage and under voltage conditions
• Hz: Output frequency for the load including high and low frequency conditions
Input
The input section is a green, yellow and red bar on a row below the output section showing the utility power source voltage and limits. The colors on the display indicate whether the power is within acceptable limits. If the voltage reading is in the green range it shows that the UPS is operating on the utility power. Yellow or red range indicates that the work is to be saved.
2. Battery Status and Load
Battery Status information provides description of the status of the Battery. Load feature gives the present load on UPS.
3. Secure Access
The Software provides secure access for a valid user to make changes in the Power Management Software Application.
4. Email Notification
User can configure Power Management software to send an email message to upto 4 people when an event occurs.
5. Data Log
Data Log provides the log of UPS parameters input and output voltage, input and output frequency, power, UPS status, output current, battery capacity, load and capacity at specified time interval.
6. UPS Settings
Power Management Software provides the way to set some UPS settings like
• Output voltage/ output frequency as per requirement.
• Change of Battery low/ battery high protection.
• Disabling/ Enabling of Buzzer.
• Change of High/ Low cut level.
• UPS Shutdown/ Restart.
7. Broadcasting Messages
User can configure Power Management Software to broadcast a notification message when an event occurs.
8. Customize Alerts
It can be used to change the text of an alert message or to change the response that system makes to an alert.
9. Delay Times
User can change the delay time for message for e.g. 10, 20, 30, 40, 50 or 60 sec.
10. Client Connection
This option disables/ enables Client-Server communication.
11. Update User Information
Under this option user can update his/her personal information like name, company name, address, phone number etc.
12. Priority based Settings
Attached equipments to the UPS may be given two levels of priority namely, Low and High. Time entered against this setting defines the time for low priority equipment to shutdown. The value for high priority equipment is double of this time.
13. UPS Scheduler Settings
'Weekly shutdown schedule' can be used to shut down all or segments of the UPS load at a certain time each day. Periods when the system is scheduled to be ON are shown in orange. Periods when the system is scheduled to be off are shown in white.
14. Server Shutdown Settings
It sets the interval between the time the Power Management Application software begins to shut down of the Windows environment and the power from the UPS shuts off.
15. View Data Logged File
User can view the Logged file at any time. Data which is logged are:
• Date
• Time
• Input and Output Voltage
• Input and Output Frequency
• Output Current
• Output Power
• Load percentage
• Total Units
• Ambient Temperature
• Capacity
• Battery Voltage
• Status
16. Connected Users List
Server lists the client's status, whether they are online or offline, client's name, priority and their IP addresses. Connected users show the number of clients online.
17. View Graphs
User can view 3 kinds of graphs
• Input & output voltage
• Input & output frequency
• Output power
This utility provides following features-
• Auto and Manual saving of graph
• Plotting of input and output voltage, input and output frequency, output power
• Maximum and minimum value over a period of time
• Plotting of data from files
• Start and End Time at which user had actually started/ ended the plotting in graph
• Printing of the graph
(B) Local client application registers and communicates with the local server.
Interpreting Main Panel
The main panel displays provides node information and information on the status of the power, UPS battery system, system operations, and communications.
The main panel is a graphical representation of the operational status of the system. Input and output voltage, input and output frequency is shown with the help of analog meters. Battery
voltage and Load % are indicated with the help of Bar Graphs, besides output current, output power and UPS capacity.
It provides detailed information regarding the present power situation. It also provides system shutdown time, review of the power event and battery management logs.
Following are the utilities provided by the software and the local client can configure the system accordingly.
1. Data view
Data view uses bar graphs and text to show the power situation. The display is divided into sections as follows:
Output
Output information shows the actual output load on the UPS. The Output section includes the
following:
• Status: Condition of the UPS battery
• % Load: Percentage of the UPS's calculated full load in use including overload conditions
• Volts: Output voltage for the load including over voltage and under voltage conditions
• Hz: Output frequency for the load including high and low frequency conditions
Input
The input section is a green, yellow and red bar on a row below the output section showing the utility power source voltage and limits. The colors on the display indicate whether the power is within acceptable limits. If the voltage reading is in the green range it shows that the UPS is operating on the utility power. Yellow or red range indicates that the work is to be saved.
2. Battery Status and Load
Battery Status information provides description of the status of the Battery. Load feature gives the present load on UPS.
3. Update Server IP
Client has the permission to change the Server IP address. Connection gets closed as soon as user would change Server IP.
4. Update Priority
Client has, by default, priority 'Low', which the Client can change. Clients are allowed to change their priority from 'Low' to 'High' and vice versa.
5. Update User Name and Password
Client can change his user name and password.
Now if the user has to monitor/ control the UPS system remotely he has to go through web monitoring. The web monitoring application includes -
1. Power Management Software reads data from the DSP of UPS through RS-
232/RJ45/USB port.
2. Similarly live data of 'N' number of UPS data are available on Server in every 3 to 10
seconds.
3. A valid user has to login on a specified website which will display list of all UPS.
4. "Details" link displays the live status and parameters of the product.
5. One can view the data log of product date & time wise.
6. One can also view the summary of the product since installed. The summary contains
blackouts, brownouts, number of units drawn by load through UPS, review of grid power
in terms of fluctuations and number of outages.
7. Blackouts contains each and every moment in the absence of mains.
8. Brownout contains duration of UPS mode when there is low voltage.
9. Other details can be viewed like:
• INPUT Voltage duration:
1. <180V
2. > 180V &< = 200V
3. > 200V &< = 230V
4. > 230V &< = 250V
5. > 250V &< = 270V
6. >270V
• INPUT Frequency duration:
1. < = 49.8 Hz
2. < = 49.5 Hz
3. < = 48Hz
4. > = 50.2 Hz
5. > = 50.5 Hz
• OUTPUT Power / Load duration:
1. <=25%
2. 26%-50%
3. 51%-75%
4. 76%-100%
5. >=101%
• Duration of Status i.e. duration of on mains/ on battery/ overload
conditions etc.
10. Charts of input voltage vs time, input frequency vs time, output voltage vs time, output
frequency vs time, battery voltage vs time, output power vs time, load vs time, blackouts
vs date are available for analysis.
11. One can send request code of particular product through mobile to retrieve live status of
product immediately.
12. Controlling can be done through Web and mobile to-

• Set Output Voltage/ Output Frequency as per requirement.
• Change Battery Low/ Battery High protection.
• Disable/ Enable buzzer.
• Change High/ Low cut level.
• Shutdown UPS/ Restart.
13. Local computers can also be controlled/ scheduled shutdown by using TCP/ IP.
ADVANTAGEOUS FEATURES
1. Highest load withstand capacity.
150% for 10 Sec
200% for 2 Sec 300% for 1 Sec
With the highest load withstand capacity; the system is best suited for SMPS load, because SMPS load draws a lot of current in the beginning. Technically this feature comes from precise and tremendous fast control of Inverter due to DSP.
2. High Power Factor in all conditions.
High power factor (>0.98) at load (25% tolOO%) with charger ON and with mains between 150V to 270V. power factor remains between 0.95 and 0.99.
This feature provides really the advantage of power factor corrections at any load and input mains voltage. Technically this feature is a result of precise design of choke including material selection for choke and gain setting of controller.
3. A separate booster for batteries having the following advantages:
a. Zero current sharing from battery bank at any load condition and mains conditions
which results in increase in battery backup time, and reliability of batteries.
b. Remarkable transient response, no disturbance in inverter output waveform when
UPS switches from mains to battery and vice versa.
c. Due single inductor boost topology which has no limit of power transfer as in the
case of other topologies.
4. SMPS charger(Constant Voltage Constant Current type)
This feature provides very low ripple charging and charging current independent of input and output voltage. This increases battery life. Further, there is no disturbance in input power factor. Technically this charger works on high frequency and precise control, due to fast control
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM:
1. DSP controlled Triple conversion online UPS with remote monitoring comprising of an
AC power input, line filter, rectifier section, power factor correction (PFC) circuit, SMPS
battery charger, a battery bank, booster choke, an inverter, IGBT driver, inverter
controller, a power supply unit (PSU), an isolation transformer, a DC bus, a bypass
circuit having a bypass switch and a power output.
2. DSP controlled Triple conversion online UPS with remote monitoring as claimed in
claim 1 wherein the battery bank is charged using a switch mode power supply (SMPS)
battery charger circuit.
3. DSP controlled Triple conversion online UPS with remote monitoring as claimed in
claim 1 or 2 wherein tfshe inverter controller includes DSP circuit, LCD driving circuit,
circuit to convert 12V DC to 5V DC, sensing circuit, a multiplier, an AC current
regulator and a pulse width modulator (PWM).
4. DSP controlled Triple conversion online UPS with remote monitoring as claimed in
claim 1 wherein the power factor correction (PFC) circuit having three separate section
(i) input power interface card (ii) PFC choke (iii) PFC & booster power module having
PFC & booster controller.
5. DSP controlled Triple conversion online UPS with remote monitoring as claimed in any
of the preceding claims wherein the PFC & booster power module comprising of DC bus
filter section, charging and passive discharge circuits, switching circuits using IGBTs and
diodes for high voltage and outstanding efficiency.
6. DSP controlled Triple conversion online UPS with remote monitoring as claimed in any
of the preceding claims wherein the UPS may be interfaced with a computer installed
with special software.
7. DSP controlled Triple conversion online UPS with remote monitoring as claimed in any
of the preceding claims having highest load withstand capacity, high power factor in all
conditions, a separate booster for batteries and SMPS charger (CVCC type) such as
herein described.
8. DSP controlled Triple conversion online UPS with remote monitoring substantially as
herein described with reference to the accompanying drawings.