Hardware Description
; r: }5 o# f; j- B$ \; n" s) r. {5 g2 T DC/AC Inverter
0 n, R9 H; L) ?; E" j2 A. f9 [4 IThe Inverter will convert from the direct current (DC) to the alternating current (AC); the converted AC could generate any voltage and frequency by requirement with transformer, switching and control circuits. After converter, the inverter will generate a nearly perfect sine wave output (<3% total harmonic distortion) that is essentially the same as utility-supplied grid power. Thus it is compatible with all AC electronic devices. This is the on-grid type inverters. The design is more complex, and costs more per unit power. The electrical inverter is a high-power electronic oscillator. It is so named because early mechanical AC to DC converters was made to work in reverse, and thus were "inverted", to convert DC to AC.0 L, E- ?6 o. C) E
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DSP Controller & MCU Controller
" l9 s v4 r" B" g2 ~The internal control is redundant built. It consists out of two controllers (U7, U9), the master DSP controller (U7) can control the relays, measures voltage, frequency, AC current with injected DC, insulation resistance and residual current. In addition it tests the current sensors before each start up. The slave MCU (U9) can also shut down the relays. Both microcontrollers communicate with each other.$ T# ?' z P0 N( W) r
; L% Q7 q) Y' e$ Y7 \ RCMU Circuit
: {* f- l) {$ `4 z% w9 z; VThe RCMU (Residual Current Measurement Unit) monitors the AC residual currents between the inverter and the output filter. The residual current also will be checked and monitored by the two controllers (Master DSP/Slave MCU) separately.4 ^) U, Z, u- E! `0 Q0 N$ X. _
7 @# m2 x0 o5 a* E$ \! l% R! ~ Grid disconnection
( Y) f! @+ j5 o' A8 I9 o/ m8 |& jThe units provide two relays in series in each phase. The relays are tested self before each start-up.
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