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Showing papers on "Maximum power point tracking published in 1999"


Journal ArticleDOI
03 Oct 1999
TL;DR: In this article, the authors investigated a hybrid multilevel power conversion system for high performance, high power applications, which consists of a hybrid seven-level inverter, a diode bridge rectifier and an IGBT rectifier per phase.
Abstract: Use of multilevel inverters is becoming popular in recent years for high power applications. Various topologies and modulation strategies have been investigated for utility and drive applications in literature. Trends in power semiconductor technology indicate a trade-off in the selection of power devices in terms of switching frequency and voltage sustaining capability. New power converter topologies permit modular realization of multilevel inverters using a hybrid approach involving integrated gate commutated thyristors (IGCT) and insulated gate bipolar transistors (IGBT) operating in synergism. This paper is devoted to the investigation of a hybrid multilevel power conversion system typically suitable for high performance, high power applications. This system designed for 4.16 kV, /spl ges/100 hp load comprises of a hybrid seven-level inverter, a diode bridge rectifier and an IGBT rectifier per phase. The IGBT rectifier is used on the utility side as a real power flow regulator to the low voltage converter and as a harmonic compensator for the high voltage converter. The hybrid seven-level inverter on the load side consists of a high voltage, slow switching IGCT inverter and a low voltage, fast switching IGBT inverter. By employing different devices under different operating conditions, it is shown that one can optimize the power conversion capability of entire system. A detailed analysis of a novel hybrid modulation technique for the inverter, which incorporates stepped synthesis in conjunction with variable pulse width of the consecutive steps is included. In addition, performance of a multilevel current regulated delta modulator as applied to the single phase full bridge IGBT rectifier is discussed. Detailed computer simulations accompanied with experimental verification are presented in the paper.

712 citations


Patent
11 Sep 1999
TL;DR: In this paper, a multi-functional power source for power tools is described, which includes an AC-to-DC converter, a voltage input selector, a DC to DC converter, an auto voltage selector, and a solid state power monitor which automatically sets the voltage and current to be delivered to power connectors integral to the multi-function power block.
Abstract: Method and apparatus for providing multi-power source for power tools. The apparatus includes (a) a multi-functional power block capable of being powered from multiple energy sources including, but not limited to, AC mains, DC power or fuel cell, and (b) a multi-functional battery module capable of receiving power from the multi-functional power block and fit into the recess in the tool which receives the power pack. The multi-functional power block includes an AC to DC converter, a voltage input selector, a DC to DC converter, an auto voltage selector, and a solid state power monitor which automatically sets the voltage and current to be delivered to power connectors integral to the multi-functional power block. The multi-functional battery module includes batteries, a battery charger which uses power from the multi-functional power block to recharge the battery, a power distributor, and a power monitor which monitors operation of the tool's motor so that the power distributor can automatically deliver the required voltage and current to the tool's motor from one or a combination of battery power and the multi-functional power block to produce the required operational driving torque. The apparatus also includes an AC mains plug and a first flexible line running from the AC mains plug to the multi-functional power block, a DC connector and a second flexible line running from the DC connector to the multi-functional power block, a third flexible line with attached DC plugs at both ends, and a series of adapters designed to fit into recesses in the multi-functional power block and in the tool.

451 citations


Journal ArticleDOI
TL;DR: A methodology for calculating the correct size of a photovoltaic (PV)-hybrid system and for optimizing its management is developed, and it is shown that battery size can be reduced by a factor of two in PV-hybrid systems, as compared to PV stand-alone systems.

262 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe the design, implementation and testing of a prototype version of a peak power tracking system for small wind turbines in battery charging applications, and show that one configuration consisting of reactive compensation by capacitors and a DC/DC converter is able to optimally load the wind turbine and thus obtain maximum energy capture over the whole range of wind speeds.
Abstract: This paper describes the design, implementation and testing of a prototype version of a peak power tracking system for small wind turbines in battery charging applications. The causes for the poor performance of small wind turbines in battery charging applications are explained and previously proposed configurations to increase the power output of the wind turbines are discussed. Through computer modeling of the steady-state operation the potential performance gain of the proposed system in comparison with existing systems is calculated. It is shown that one configuration consisting of reactive compensation by capacitors and a DC/DC converter is able to optimally load the wind turbine and thus obtain maximum energy capture over the whole range of wind speeds. A proof of concept of the peak power tracking system is provided by building and testing a prototype version. The peak power tracking system is tested in combination with a typical small wind turbine generator on a dynamometer. Steady-state operating curves confirming the performance improvement predicted by calculations are presented.

229 citations


Proceedings ArticleDOI
27 Jun 1999
TL;DR: In this article, a new maximum power point tracker (MPPT) approach is presented that allows minimization of the drawback caused by the intrinsic capacitance of the photovoltaic array (generally neglected) giving the possibility of operation with a large degree of freedom, independent from the converter topology and photovolastic power generator, electrical network and technology.
Abstract: The present trend for commercial telecommunication and scientific satellites is the utilization of standard platform, characterized by a high level of flexibility and reduced nonrecurring costs. One of the areas where flexibility is mandatory is the electrical primary power subsystem, due to the impact on solar array configuration and dimensions and on power conditioning unit. Use of the maximum power point tracker (MPPT) concept allows optimization of the above mentioned subsystem, maximizing the power transfer from the photovoltaic generator. The purpose of the paper is to present a new MPPT approach that allows minimization of the drawback caused by the intrinsic capacitance of the photovoltaic array (generally neglected) giving the possibility of operation with a large degree of freedom, independent from the converter topology and photovoltaic power generator, electrical network and technology.

151 citations


Proceedings ArticleDOI
03 Oct 1999
TL;DR: In this article, the authors proposed a new MPPT (maximum power point tracking) control scheme for a PV array based on the principle of power equilibrium at the DC link, which needs no detection or calculation of the power and no decision making logic or look up tables, except for several numbers of operational amplifiers.
Abstract: This paper proposes a new simple MPPT (maximum power point tracking) control scheme for A PV (photovoltaic) array based on the principle of power equilibrium at the DC link. In contrast to the typical conventional MPPT scheme based on the so-called mountain climbing method, the proposed scheme needs no detection or calculation of the power and no decision making logic or look up tables, except for several numbers of operational amplifiers. Its operation principle is explained quantitatively. In order to confirm the availability of the scheme, a simulation study using general purpose circuit simulation software PSIM and an experiment have been carried out. Although the stability study and system design are left for future study, the validity of the proposed new MPPT method has been clarified through the simulation and experimental results.

132 citations


Journal ArticleDOI
01 Sep 1999
TL;DR: In this paper, the authors describe the analysis, modelling and implementation of a fuzzy based photovoltaic peak power tracking system, which is implemented by an inexpensive RISC microcontroller.
Abstract: The authors describe the analysis, modelling and implementation of a fuzzy based photovoltaic peak power tracking system. The maximum power of a photovoltaic system changes with temperature, solar intensity and load. An analytical model is built for the solar cell on the basis of the manufacturer's characteristics. The solar panel is integrated with the converter model and a fuzzy algorithm is developed, so as to perform an online search procedure to track the maximum power continuously. The system is implemented by an inexpensive RISC microcontroller. Experimental results have shown excellent performance, robustness with parameter variation and modularity for parallel operation at higher power. The system is ready and easy to fit into existing installations.

118 citations


Journal ArticleDOI
TL;DR: In this paper, a combined RBF and backpropagation network is used to predict the effects of passing clouds on a utility-interactive photovoltaic (PV) system with battery storage.
Abstract: In this paper, a combined radial-basis-functions (RBF) and backpropagation network is used to predict the effects of passing clouds on a utility-interactive photovoltaic (PV) system with battery storage. Using the irradiance as input signal, the network models the effects of random cloud movement on the electrical variables of the maximum power point tracker (MPPT) and the variables of the utility-linked inverter over a short period of time. During short time intervals, the irradiance is considered as the only varying input parameter affecting the electrical variables of the system. The advantages of artificial neural network (ANN) simulation over standard linear models is that it does not require the knowledge of internal system parameters, involves less computational effort, and offers a compact solution for multiple-variable problems. The model can easily integrated into a typical utility system and resulting system behavior can be determined. The viability of the battery-supported PV power system as a dispatchable unit is also investigated. The simulated results are compared with the experimental results captured during cloudy days. This model can be a useful tool in solar energy engineering design and in PV-integrated utility operation.

111 citations


Patent
21 Jun 1999
TL;DR: In this article, the authors proposed a method for determining photovoltaic module temperature by combining irradiance data, input DC current and voltage measurements and the knowledge that the inverter is operating at a known point on a module IV curve for a given set of temperature and irradiance conditions.
Abstract: An inverter includes a first switch to disconnect an output of the inverter from any device connected thereto, a second switch to disconnect and connect an input of the inverter from direct current fed to the inverter, and a discharge device to discharge any residual charge on a large capacitor. The inverter further includes a voltage sensor to measure input DC voltage to the inverter, a current sensor to measure input DC current to the inverter and a data recorder to provide a current voltage trace to provide a current-voltage curve tracer to provide current-voltage properties of the solar array to which the inverter is attached. The inverter is capable of reproducibly operating at the same point on a module IV curve for a given set of temperature and irradiance conditions. By coupling a temperature sensor to the inverter, photovoltaic module temperature can be measured and combined with the data from the input DC current and voltage sensors and information on the photovoltaic module operating characteristics to compute solar plane-of-array irradiance. Also described is a method for ascertaining photovoltaic module temperature by combining irradiance data, input DC current and voltage measurements and the knowledge that the inverter is operating at a known point on an IV curve. The inverter also includes AC current and voltage sensors for computing inverter output total harmonic distortion.

103 citations


Proceedings ArticleDOI
29 Nov 1999
TL;DR: In this paper, the authors proposed a novel maximum power point controller, which not only can track the maximum power of an array quickly without perturbation and observation process but also can be implemented easily.
Abstract: In this paper, the authors proposed a novel maximum power point controller, which not only can track the maximum power of an array quickly without perturbation and observation process but also can be implemented easily. The main idea is based on the graphical interpretation of the maximum power point as the intersecting point of two curves on the phase plane corresponding to the solution of two algebraic equations. In other words, the operating point is the intersecting point of the PV-array characteristic curve and the maximum power line. A circuit is constructed based on a boost circuit and a three phase full bridge inverter.

102 citations


Patent
24 Feb 1999
TL;DR: In this paper, the virtual optimum operating voltage, the MPPT minimum voltage, MPPT maximum voltage, and the low and high voltage change width switching voltages used when MPPT control is carried out are calculated on the basis of the output voltage of a solar panel immediately before the startup of the inverter circuit in the solar power generating device and MPPT controller was carried out on each of the calculated voltage values.
Abstract: In order to obtain a solar power generating device capable of effectively using power generated by a solar cell, the virtual optimum operating voltage, the MPPT minimum voltage, the MPPT maximum voltage, and the low and high voltage change width switching voltages used when MPPT control is carried out are calculated on the basis of the output voltage of a solar panel immediately before the startup of the inverter circuit in the solar power generating device and the MPPT control is carried out on the basis of each of the calculated voltage values.

Proceedings ArticleDOI
29 Nov 1999
TL;DR: In this paper, a transformer-less single phase inverter for a photovoltaic (PV) power system is presented, which consists of two sets of a PV array and buck-boost type chopper circuit.
Abstract: This paper presents a newly developed transformer-less single phase inverter for a photovoltaic (PV) power system. The proposed system consists of two sets of a PV array and buck-boost type chopper circuit. However, it is afraid that the system has lower "using rate" of PV energy than that of the ordinary PV system, as each PV array is only operated in the half duration of the AC power frequency. In this paper, it is also discussed how to increase this "using rate" by varying the connected capacitor between PV array terminals. The perturbation and observation method is adapted to the maximum power tracking in our PV systems. We adopt the wavelet transform to detect a power outage. The experimental data shows that this new inverter can supply AC power to the utility grid line with the power factor nearly unity.

Patent
02 Aug 1999
TL;DR: In this paper, the power saving for an uninterruptible power system (UPS) itself or a total system including all load associated with a UPS has rarely been considered, and had the necessity of improvement.
Abstract: The power saving for an uninterruptible power system (UPS) itself or a total system including all load associated with a UPS has rarely been considered, and had the necessity of improvement. Therefore, a UPS is provided which comprises a power input means (1) for supplying commercial power to the system, an AC/DC converter (4), a rechargeable battery (6), a charger circuit (5), a DC/AC inverter (8), a control circuit (9) for performing various controls of the system, a power supply circuit (3) for transmitting the output from the power input means (1) to the control circuit (9), a switch (a2) connected with the power input means (1), and a switch (b12) for switching power supply lines.

Proceedings ArticleDOI
01 Jan 1999
TL;DR: This design calls for a pilot module to track the maximum power point voltage by changing the duty cycle of a step-down chopper, which is controlled by a software P voltage controller.
Abstract: A design of an inexpensive and efficient maximum power point tracker is presented. This design calls for a pilot module to track the maximum power point voltage (V/sub m/). The tracking is done by changing the duty cycle of a step-down chopper, which is controlled by a software P voltage controller. The controlled voltage of the tracker (V/sub m/) is obtained by measuring the open circuit voltage (V/sub oc/) and searching in the look-up table stored in the computer for (V/sub m/) versus the measured (V/sub oc/). This table is obtained from theoretical calculations for maximum power points locus of the solar cell array (SCA) used. For the difference between the theoretical and experimental locus of the maximum power points, for temperature effect, degradation of the (SCA) and dust effect, the oscillation about the theoretical point is used to determine the actual point. It is also used for the (power-voltage) curve of the SCA.

Patent
09 Jun 1999
TL;DR: In this article, a power supply voltage sensor generates a signal to a power manager, which configures the camera into a lower power consumption state, until the power source is exhausted.
Abstract: A power supply provides a voltage to a digital camera. If the power supply voltage falls below a predetermined threshold, a voltage sensor generates a signal to a power manager. In response, the power manager configures the camera into a lower power consumption state. As the power source weakens further, the power manager continues to place the camera into a lower and lower power consumption state, until the power source is exhausted. The method of the present invention preferably comprises the steps of monitoring the power source's voltage, generating a signal if that voltage falls below a pre-determined threshold, and reducing the camera's power consumption in response to the signal.

Patent
30 Jul 1999
TL;DR: In this article, a circuit and method for charging batteries while a power supply also powers a dynamically varying load is presented, which advantageously allows the load to change from external power to battery power without switching delays.
Abstract: A circuit and method for charging batteries while a power supply also powers a dynamically varying load. All power in excess of that required by the load is used by a power converter to charge the batteries. The circuit advantageously allows the load to change from external power to battery power without switching delays.

Journal ArticleDOI
TL;DR: In this article, a power conditioner for medium-size photovoltaic generators is proposed, which employs several poles of the 3-level inverter, which, configured through current sharing reactors, can provide a multi-level voltage.
Abstract: This paper describes the fundamental design of a novel power conditioner for medium size photovoltaic generators. The proposed conditioner employs several poles of the 3-level inverter, which, configured through current sharing reactors, can provide a multi-level voltage. The conditioner provides maximum power point tracking and power factor correction by direct control of the instantaneous value of the inverter output current. A PWM-gate control is derived which utilizes the multilevel form of the output voltage and effectively increases the switching frequency of the inverter without increasing the switching frequency of its valves. Simulation studies in the paper verify the steady state and transient performance of the proposed conditioner. The simulation results show that implementation of the proposed design could significantly improve the power quality of photovoltaic generators.

Patent
20 Dec 1999
TL;DR: In this paper, maximum power point tracking is realized without employing a DC/DC converter by keeping optimal operating conditions of an inverter from the waveform of pulse voltage and current generated from solar cells when the instantaneous output power from the inverter varies over time.
Abstract: PROBLEM TO BE SOLVED: To solve the problem in an AC output solar cell power generating system for taking out maximum power from solar cells and superimposing it on the power from an AC power supply, that the power conversion loss is increased because power is converted twice when a DC/DC converter having a maximum power point tracking function is combined with an inverter in order to realize maximum power point tracking and total efficiency of the power generating system is lowered. SOLUTION: Maximum power point tracking is realized without employing a DC/DC converter by keeping optimal operating conditions of an inverter from the waveform of pulse voltage and current generated from solar cells when the instantaneous output power from the inverter varies over time.

Proceedings ArticleDOI
29 Nov 1999
TL;DR: In this paper, a new inverter for a utility interactive photovoltaic system is proposed, which consists of the DC converter that generates the single phase absolute value of sinusoidal current and a square wave voltage inverter which synchronizes with the AC power source.
Abstract: In this paper, a new inverter for a utility interactive photovoltaic system is proposed. This system consists of the DC converter that generates the single phase absolute value of sinusoidal current and a square wave voltage inverter which synchronizes with the AC power source. This DC converter consists of two switching devices and a capacitor for a nondissipative snubber circuit. The DC converter is applied to a pulse width modulation to obtain absolute value of sinusoidal current. It is not necessary to set the dead time of the switching devices in generating waveforms. Therefore, we can regard the dead time effects as small. The inverter is switched by the AC power source frequency so the line noise of voltage and current caused by the high frequency switching is very small. In this paper, it is confirmed by simulation that the proposed inverter for a new photovoltaic system has stable operation and good output characteristics are obtained by the experimental results.

Proceedings ArticleDOI
09 Jun 1999
TL;DR: In this article, a static conversion system for treatment of the solar energy from photovoltaic panels is presented, which is interconnected with the mains power supply, contributing to the generation of the electrical energy.
Abstract: This paper presents the analysis of a static conversion system for treatment of the solar energy from photovoltaic panels. This system is interconnected with the mains power supply, contributing to the generation of the electrical energy. The power structure is composed by a current-fed push-pull converter, a buck converter and a current inverter. The main features of the system are: simple control strategy, robustness, lower harmonic distortion of the current and natural isolation. The principle of operation, design procedure and experimental results are presented.

Patent
04 Feb 1999
TL;DR: In this article, a control method using calculation of the power characteristic (B) from a quasi-continuous current characteristic (A) of a sensor of similar type and charge to the solar generator, which is isolated from the latter, with provision of a setting parameter for the generator transducer in dependence on the maximum power point (MPP) of power characteristic.
Abstract: The control method uses calculation of the power characteristic (B) from a quasi- continuous current characteristic (A) of a sensor of similar type and charge to the solar generator, which is isolated from the latter, with provision of a setting parameter for the solar generator transducer in dependence on the maximum power point (MPP) of the power characteristic. An Independent claim for a maximum power point control circuit is also included.

Patent
08 Jun 1999
TL;DR: In this article, the output power-output voltage characteristic of a solar battery has a plurality of peaks without making the output voltage and output power of the solar battery fluctuate needlessly.
Abstract: PROBLEM TO BE SOLVED: To provide a solar power generating device having a maximum power point tracking function capable of accurately detecting a maximum power point even when the output power-output voltage characteristic of a solar battery has a plurality of peaks without making the output voltage and output power of the solar battery fluctuate needlessly. SOLUTION: An output power-output voltage characteristic detecting means CD1 provided with a solar battery PV1 having the same environmental condition as a main solar battery PV2 is provided apart from a main generation circuit. Then, an output voltage controlling means CT1 obtains the numerical data of the output power-output voltage characteristic of the battery PV1 for characteristic detection by turning a switch SW on or off and detects a maximum power point. Then, control signals S1a to S1d are given to respective transistors T1 to T4 of a voltage type inverter IV1 so that the main solar battery PV2 can generate a voltage value corresponding to the detected maximum power point.

Patent
26 Aug 1999
TL;DR: In this paper, a line power unit controller receives a power level command and controls a main inverter that draws DC power from a DC bus to deliver the commanded power to a grid.
Abstract: A line power unit controls electrical power delivery to a grid from a three phase permanent magnet generator. A line power unit controller receives a power level command and controls a main inverter that draws DC power from a DC bus to deliver the commanded power to a grid. The DC bus is fed DC voltage via a three phase permanent magnet generator and a rectifier. The inverter delivers power to the grid via a filter, transformer and main contactor. The line power unit controller also controls the main contactor to break the connection with the grid. A precharge circuit draws power from the grid to precharge the DC bus to a precharge voltage. Alternatives include a start inverter separate from the main inverter that permits simultaneous delivery of power to the grid and commutation of the permanent magnet generator as a motor to spin an engine connected thereto at a speed sufficient to permit engine starting. Another alternative utilizes a single inverter for engine starting and power delivery which does not permit these operations to be simultaneously performed. Further alternatives include eliminating the transformer by utilizing a high-voltage rated main inverter.

Patent
29 Apr 1999
TL;DR: An uninterruptible power system (10) in which separate inverters (A, B, C) are connected to separate d.c. power sources (16, 42, 64) established by independent power supplies.
Abstract: An uninterruptible power system (10) in which separate inverters (A, B, C) are connected to separate d.c. power sources (16, 42, 64) established by independent power supplies, a.c., d.c. or both, and have their a.c. outputs connected to separate transformer primary windings (36, 62, 86) with the primary to secondary turns ratios of the primary windings establishing different effective secondary voltages for determining the power source for normally supplying the power from the system (10) and the sequence in which the other power sources are used on power failure, the magnitudes of the effective voltages determining the power source for initially supplying the power with any other power source supplying the power when its effective voltage is higher than any other available power source.

Patent
14 May 1999
TL;DR: In this paper, the authors proposed a current type inverter for photovoltaic power generation having low loss and high conversion efficiency in which the number of electronic parts passing a high frequency current is decreased while reducing noise.
Abstract: PROBLEM TO BE SOLVED: To provide a current type inverter for photovoltaic power generation having low loss and high conversion efficiency in which the number of electronic parts passing a high frequency current is decreased while reducing noise. SOLUTION: The current type inverter 10 for photovoltaic power generation comprises a bridge type switching circuit 36 comprising four semiconductor switching elements 28-34 connected, respectively, in series with diodes 20-26 receiving DC power from a solar cell array section 12 through a reactor 18, and a current type inverter section 14 having a PWM control circuit 38 outputting a switching control signal to each semiconductor switching element 28-34 wherein DC power is converted into AC power through the current type inverter section 14 and linked with a commercial power system. The reactor 18 is divided uniformly into two and arranged symmetrically to the solar cell array section 12 and a high frequency semiconductor switching element 40 is connected to the input side of the switching circuit 36 in parallel therewith.

Patent
12 Mar 1999
TL;DR: In this article, phase detection was used to automatically and substantially equalize the currents supplied to a load by each of the variable-frequency power sources, and to cancel a ripple component of the input current drawn by the system.
Abstract: A system and a method may use variable-frequency power sources for supplying power to a load The system and method use phase detection in order to automatically and substantially equalize the currents supplied to a load by each of the variable-frequency power sources, and to cancel a ripple component of the input current drawn by the system First and second power sources supply power to the load The power sources have a similar relationship between their respective variable switching frequencies and the power that they supply to the load First and second switching frequencies of, respectively, the first and second power sources are locked to one another using phase detection to substantially equalize the power supplied to the load by each power source The system and method are advantageously utilized to provide a power factor correction front-end for a switch-mode power supply Power sources with non-linear and/or inverse relationships between power supplied and switching frequency can be used In alternate embodiments power from series power sources is equalized by equalizing voltages supplied by each power source to a load

01 Jan 1999
TL;DR: In this article, the photovoltaic (PV) voltage varies nonlinearily with temperature and isolation level, but is directly proportional to the PV cell open circuit voltage.
Abstract: It is shown that at maximum power, the Photovoltaic (PV) voltage varies nonlinearily with temperature and isolation level, but is directly proportional to the PV cell open circuit voltage. The proportionality voltage-factor is fixed for a given PV generator regardless of temperature, isolation and panel configuration, but depends on cell material and manufacturing. This remarkable property is used to achieve temperature and insolation independent maximum power point tracking of satellite’s solar cells with a simple and reliable technique. The open circuit voltage is continuously measured by a microcontroller and is used to estimate the maximum power operating point of the system.

Patent
20 Jan 1999
TL;DR: In this paper, a D/A convertor for a pump driven by a photocell is characterized in that a maximum power point tracking circuit and a drying protection circuit are also arranged.
Abstract: The utility model relates to a D/A convertor for a pump driven by a photocell, comprising a casing 1, a on-off power supply circuit 2 arranged in the casing, a PWM frequency conversion control circuit 4, a protection control circuit 5, a level shift circuit 6, an overheat protection circuit 7, an excess voltage protection circuit 8, an over current short protection circuit 10, a drive circuit 11, a main circuit 12, a current sampling circuit 13, a photoelectric isolation circuit 14, and a manual on-off circuit 15. The D/A convertor for a pump driven by a photocell is characterized in that a maximum power point tracking circuit 3 and a drying protection circuit 9 are also arranged. The utility model can extract the maximum power from a solar cell array at any time, and has a drying protection function.

Patent
22 Jun 1999
TL;DR: In this article, a power storing system is provided with a battery 5 and a bidirectional inverter 4, which converts the AC power of commercial power supply into a direct current and the DC output of the battery 5 into an alternating current.
Abstract: PROBLEM TO BE SOLVED: To provide a power storing system which enables a user to use economical nighttime power without waste. SOLUTION: A power storing system is provided with a battery 5 and a bidirectional inverter 4, which converts the AC power of commercial power supply into a direct current and the DC output of the battery 5 into an alternating current, stores the AC power of the commercial power supply in the battery 5, and supplies the power stored to electrical equipment. The system is also provided with a control section 33, which stores several types of one-day discharge patterns of the battery 5 in advance so that the user of the system can select the patterns and controls the one-day discharge pattern of the battery 5. When the power storing system is constituted in this way, the user can effectively use economical nighttime power charged in the battery 5 without waste, because the using pattern of the nighttime power can be set in accordance with the daily living pattern of the user. Consequently, the electricity charges to the user can be reduced, and power loads can be leveled.

Patent
08 Oct 1999
TL;DR: In this paper, a power distribution sub-system distributed power from n+m (e.g. 3) power supply units within a system unit, where n and m are integers and n power supply devices are required to power the system.
Abstract: A power distribution sub-system distributed power from n+m (e.g. 3) power supply units within a system unit, where n and m are integers and n power supply units (e.g. 2) are required to power the system. The power supply units are connectable to a common power rail. A current sensor detects a current greater than n*Imax, where Imax is the maximum power output of a power supply unit. The current sensor outputs an overcurrent signal when the sensed current exceeds n*Imax. In response to this overcurrent signal, a controllable shunt operates to shunt the power rail to ground, thereby discharging any stored charge. A power distribution board, which forms part of a power sub-frame assembly, carries the power distribution sub-system. The system unit can be a rack-mountable computer system unit for a telecommunications.