DE202010001342U1 - String charge controller for direct charging of accumulators on series-connected photovoltaic modules (strings) with high output voltage - Google Patents

Abstract

Control unit for directly charging accumulators on photovoltaic modules connected in series, characterized in that the string voltage is measured and, when a voltage threshold is reached, the voltage is converted to a lower value. The maximum energy output from the photovoltaic modules is determined (maximum power point) and a conversion into a suitable accumulator charging characteristic is effected.

Description

concept

basic function the string loader (in drawing unit SLR) is the direct one Implementation of a high DC voltage, connected in series Photovoltaic modules (in drawing unit A) is generated in one adapted charging current for Accumulators (in drawing unit F). The main advantage across from other technologies is the direct charge of the accumulators, without multiple implementation by power inverter and power chargers, for example.

In order to It is possible to build photovoltaic systems that consist of a module field From photovoltaic systems, either a direct mains supply via commercial mains inverters allow and / or the direct storage of energy in a battery pack enable.

PV feed-in inverter have an input voltage of about 350 V DC-750 V DC. The string charge controller processes the same input voltage and can therefore be parallel to the PV grid feed inverter be connected to the photovoltaic module array. The direct connection to the photovoltaic module array is also possible. With this solution is it also possible existing photovoltaic systems that only carry out mains supply functional to expand.

function Description

Of the DC-DC converter (GGU / in drawing unit B) converts the Output voltage of the photovoltaic modules by means of DC-DC converter in a lower DC voltage. These are buck converters or forward converter used. Use both circuit variants Low-resistance semiconductor switching elements, such as MOSFETs, Thyristors or the like.

At the Flow converter will be the DC input voltage, for example through bridge circuits converted into an AC voltage and by one or more transformers transformed into a lower AC voltage, which in turn is rectified.

The Control of DC-DC converter (GSU control / in drawing Unit C) regulates the voltage conversion so that the photovoltaic modules the maximum power is withdrawn (maximum power point regulation). This is about several operating points determines the optimum voltage-current combination.

Of the Flow converter preferably operates at high switching frequency, which the size and with it also the costs of transformers are minimized. Typical switching frequencies here are 20 kHz to 50 kHz.

Of the Accumulator controller (ALR / in drawing unit D) sets the voltage provided by the DC converter Voltage into a charge function, which for the respective technology of the Accumulators is adjusted. The accumulator controller is thus the burden for the DC-DC converter. When the charging function is active, it flows Electricity from the photovoltaic modules, through the string charge controller and the accumulators.

The Control of accumulator charge controller (ALR control / In drawing Unit E) regulates the optimal charging function of the accumulators. It can be done accordingly the accumulator technology special functions are implemented. The accumulators essentially provide a voltage-dependent load for the ALR. Also in the ALR semiconductor switching elements are used, the in principle, switch the output of the GSU to the accumulators. at Reaching the full charge state, the connection of the GSU Output to the accumulators separated. The ALR control can then a message to a higher-level controller supply, so that in this case the photovoltaic modules again exclusively on direct mains supply can be switched.

Either the HSE control as well as the ALR control are software controlled. The software is based on commercial Microcontrollers executed. It is also possible, the function of the string load controller by external control units to influence. This concerns specifically possible options such as voltage or charge state monitoring.

All Parameters are adjustable.

Overview the drawing elements:

• - A: Photovoltaic modules connected in series
• - B: DC-DC converter - GSU
• - C: Control of the DC-DC converter - GSU control
• - D: Accumulator controller - ALR
• - E: Control of the accumulator controller - ALR control
• - F: accumulators

Claims (6)

Control unit for direct charging of accumulators connected in series photovoltaic modules, characterized in that the string voltage is measured and upon reaching a voltage threshold, the implementation of the voltage in a lower value takes place. The maximum energy output from the photovoltaic modules is determined (maximum power point) and a conversion into a suitable accumulator charging characteristic is effected. Control unit according to Claim 1, characterized that they also process input voltages in the range of more than 350 V DC can. Control unit according to Claims 1 and 2, characterized that the function is dependent is the state of charge / voltage of the accumulators and the output power the series-connected photovoltaic modules. Control unit according to Claims 1, 2 and 3, characterized that function through a parent Control is influenced. Control unit according to claim 1, 2, 3 and 4, characterized characterized in that an adaptation to special accumulator technologies possible is, preferably software-controlled. Control unit according to claim 1, 2, 3, 4 and 5, characterized characterized in that an active load control is possible, which allows the accumulators connected to the string charge controller also parallel to Operation of a network inverter to load.