1 INTRODUCTION
China's vast land area in the northwest, solar and wind energy resources are very rich, solar radiation intensity for the annual 6000 ~ 8400 MJ/m2, the average annual solar illumination time for the 3000 ~ 3200 h; wind an average of five to six. Northwest remote areas of economic underdevelopment, and households are scattered, as if these users with electricity, the cost is too high, thus, how to make rational use of available resources - solar and wind energy to solve these problems become an effective way.
2 wind, light complementary household power systems
Diagram of the structure as shown in Figure 1.
The system can use solar and wind energy to the battery charge, will naturally be converted into chemical energy stored in batteries, then the chemical can reverse a 220 V AC power supply users, but also directly to solar and wind power inverter for 220V AC power supply users.
3 system hardware circuit
The system includes the hardware circuit main circuit, isolation and drive circuit and control circuit.
3.1 The main circuit
The main circuit topology shown in Figure Figure 2 know from the main circuit includes a charge of the battery and inverter circuit protection circuit. Map uFP said after the fan rectifier output voltage, uSP that solar output voltage, K for electromagnetic relays, GB to 24 V rated voltage of the battery.
3.1.1 overcharging the working principle of protection circuit
When the battery voltage too high when, A voltage will be greater than the reference voltage TL431 value Uref (= 2.5V) so that on-TL431, B point was to clamp low, V1 deadline, C for the high-point , V3-on, V2 deadline, D for the high-point, at this time VT14 both on-and VT15, K relay action. According to Fan solar cells and the characteristics of the solar cell output voltage directly short-circuit, fans of high-power output voltage through the uninstall resistance R9 dumping Fangdiao the contrary, when the battery voltage is too low when, VT14 and VT15 are closing, the sun Fans can batteries and the output voltage to the battery charge.
3.1.2 inverter circuit
A single-phase full-bridge inverter circuits, with power MOSFET as the inverter circuit switching devices. Power MOSFET is a multi-voltage electrical conductivity of the Unipolar-control devices, a switch moves fast and input impedance, power-driven small and no secondary breakdown, the driver circuit simple, safe working area, such as major advantages, especially As a positive temperature coefficient, can automatically balanced current, so in the importation of low-voltage, the current major power inverter system can be several power MOSFET parallel to increase current capacity. In this system, the power MOSFET will be three parallel so that the current capacity increased to three times. Inverter will rectifier after the DC voltage into the SPWM specific frequency waves, inductors and capacitors to filter through its conversion to 220 V standard sine wave voltage, which ICP transformer sub instead of the leakage, so that in this way Simple structure, low noise, and can effectively curb the wave of high harmonic components.
SPWM control mode in advance to the 0 ~ 360 ° Sine made in the form of the EPROM. Since switching signal is driven by a sine wave signal and reference triangular carrier signal generated by comparison with each other, often divided into two Unipolar and bipolar situation. Switching frequency in the same circumstances, as bipolar SPWM control of the sine wave, harmonic content and switching losses are greater than Unipolar, it is the system used in Unipolar SPWM control.
3.2 system of segregation and the drive module
Isolation and drive circuit chip output is Intel80C196MC SPWM signal to the isolation, amplification, a driver of the power switching devices moves signal the circuit. The system uses Toshiba's production company dedicated to the power MOSFET driver and IGBT gate of the isolation driver chips TLP250, its structure diagram as shown in Figure It is a photoelectric coupled device, but different from the ordinary Optocoupler, because of its output level is the push-pull circuit Larger output, it can not only former vice-isolation, but also drive capability, particularly suited to drive Medium-power MOSFET and IGBT. At the same time, the application from the hardware in order to prevent the same reliable bridge arm of the two power devices through from top to bottom, it will drive the same bridge arm of the two power devices TLP250 feet 2 and 3 feet butt each other, forming interlocking circuit So as to effectively prevent the bridge arm power devices through failure. Figure 4 specific circuit.
3.3 control circuits and control chips
Mainly through the control circuit for DC current, DC voltage, AC current, AC voltage signal detection, and the over-voltage, under-voltage, over current, the discharge, such as time limits and anti-overheating protection. Control of the microprocessor chip used Intel80C196MC.
Intel80C196MC is Intel Corporation in 1992 introduced a real 16-bit microcontroller, as the chip integrates a rather unique waveform generator (WG) units, thus greatly simplifying the SPWM for a wave of software and external hardware Circuit. Waveform generators are three separate modules, each module contains a numerical comparison, compared register, compared buffer, no time signal generator and a programmable output drive channel. Three-phase waveforms have a common carrier frequency and the common dead time, programmable for the triangular wave modulation or sawtooth modulation, once activated only require changes in the PWM duty cycle when to intervene, and the remaining time does not occupy CPU.
Waveform generators from generators at the base, access and control of the driver protection circuit.
When PWM waveform-generator for the establishment of carrier cycle. 80C196MC aggravated by loading register (WG-RELOAD) read into the data to determine the length of the carrier cycle, because
This user can change in the process of re-loading register to change the value of carrier-cycle value.
Phase PWM waveform drive channel determine the duty cycle. Each phase has its own drive channel compared to buffer (WG-COMPX), under normal circumstances, PWM waveform from the duty cycle work, register and re-loading compared to buffer these three areas to decide.
Control circuit, including control register (WG-CONTROL) and the output register (WG-OUT). At the same time, CPU internal There is also a protection circuit for monitoring EXTINT input, in order to deal with abnormal situations.
In addition, no time signal generator circuit waveform generator is a very important function, can be used to prevent a complementary PWM signal at the same time effectively, thus avoiding the same bridge arm of the power of two from top to bottom through the same time, the user can Software to the WG-CON register into the low 10 to arbitrarily set a number of non-signal time.
4 Systems Control Theory
Control systems using current feedback, voltage feedforward and feedback voltage combination of composite control, current feedback, the feedback voltage regulator with digital PI, in order to achieve steady output of the system without static poor; PI control is the moment of sampling error of Ratio (P), points (I) through a linear combination of control, the object control, PI controller for the transfer function:
Type in: Kp - the proportion coefficient;
TI - constant integration time.
WG interruption in the current feedback when completed, the current regulation a very short time, greatly increasing the speed of the dynamic response of the system and inhibit the overshoot. One current regulation time t approximately as follows:
t = (20/196) × 5 × 8ms ≈ 4 ms
This shows that the system output voltage in less than 1 / 4 fundamental cycle can resume normal.
5 system software design
Some of the major system software, including the main program, WG interrupt proceedings, PI-conditioning routines, and so on. The main program is the main task of initialization, fault judgement, the judgement and wait for the operation of signal interruption, the main program diagram shown in Figure 5.
6 Conclusion
Under the control of the design ideas 1 kW prototype, tested, Efficiency ≥ 85%, the output voltage to 220 (1 ± 4%) V, the output voltage frequency of 50 (1 ± 0.5%) Hz, and the system has been pressure, Undervoltage, overheated, over-current, short circuit and the time limits and other anti-perfect protection. No-load voltage waveform shown in Figure 6. At present, the system has been in Kaifeng City in the Yellow River He Wuju running nearly six months in good condition.
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