Design and implementation of solar power fed permanent magnet synchronous motor with improved DC-DC converter and power quality improvement using shunt active filter for reducing vibration in drive for industrial applications

2.1. Proposed converter modes of operation

Switching state 0: Power semiconducting switch $\left(S_2\right)$ turns “ON”, Power semiconducting switch (𝑺𝟏) turns “OFF”, the inductor $\left(L_1\right)$ starts discharging through the current flowing across it. At this instant of time as a result inductor $\left(L_1\right)$ charges the Intermediate Capacitor $\left(C_1\right)$. Accordingly, Intermediate Capacitor $\left(C_1\right)$ gets energized illustrated in Figure 3(a).

Switching state 1: Power semiconducting switch $\left(S_1\right)$turns “ON”, applied voltage current starts discharging. Accordingly, the inductor $\left(L_1\right)$ starts charging through the energy transmitted across it. At this instant of time as a result inductor $\left(L_1\right)$ charges the Intermediate Capacitor $\left(C_1\right)$ as shown in Figure 3(a). Concurrently, electrons in the in between capacitor $\left(V_{dc}\right)$ drops starts deenergizing. Accordingly, solar charges Inductor $\left(L_1\right)$ and the Intermediate Capacitor $\left(C_1\right)$ charges the output voltage balancing capacitor $\left(C_{02}\right)$ and it gets energy as illustrated in Figure 3(b).

Switching state 2: Power semiconducting switch $\left(S_1,S_2\right)$ turns “OFF” electrons in the inductor $\left(L_1\right)$$\left(V_{dc}\right)$ drops starts deenergizing. As a result, Inductor $\left(L_1\right)$ charges the output voltage balancing capacitor $\left(C_{01}\right)$ with diode ($D_1$), illustrated in Figure 3(c).

The efficiency of system is indirectly proportional to the total power losses. The total power losses, in the proposed converter, are the conduction, switching, diode and inductor losses. Occurrence of the conduction losses is due to the declining voltage across the device as well as the current flow through the device striking in chorus. Switching losses are sustained by the concurrent occurrence of voltage and current on the device while switching. The key waveforms of proposed converter are shown in Fig. 3(b). $I_{in}$, $i_{L1}$, $i_{D1}$, $i_{D2}$, and $i_{C1}$ are the current through the input supply, inductor $\left(L_1\right)$, diodes $\left(D_1\right)$ and $\left(D_2\right)$, and capacitor $\left(C_1\right)$ respectively [20].

Fig. 3a) Modes of operation, b) converter parameters [20]

a) Summary: conduction of circuit. Switching state 0: Inductor $\left(L_1\right)$ charges the Intermediate Capacitor $\left(C_1\right)$. Switching state 1: Solar charges Inductor $\left(L_1\right)$ and the Intermediate Capacitor $\left(C_1\right)$ charges the output voltage balancing capacitor $\left(C_{02}\right)$. Switching state 2: Inductor $\left(L_1\right)$ charges the output voltage balancing capacitor $\left(C_{01}\right)$ with diode $\left(D_1\right)$

b)

2.2. Losses in inductor and diode

The TPC used PMSM motor drive with single stage conversion system is illustrated in Fig. 5. The newly introduced system consists of PV powered proposed converter, B4-Inverter fed PMSM motor and battery powered bidirectional converter that function as a backup supply for the load operating under demand condition. As the proposed converter proposed comprises of BB switch ($S_1$), power sharing switch ($S_2$), two power diodes ($D_1$ and $D_2$), a single BB inductor ($L_1$), intermediate capacitor ($C_1$), and output capacitors ($C_{01}$ and $C_{02}$). Similarly, the bidirectional BB converter consists of buck switch ($S_3$), boost switch ($S_4$) and power diodes ($D_3$ and $D_4$). On the output side, the rear end B4-inverter includes four switches ($Q_1$ to $Q_4$) and a PMSM motor. Fig. 5 illustrates an alternate proposal of Fig. 4 i.e., TPC converter for the implementation of PMSM motor drive with single stage conversion system. The battery powered converter circuit coupling at dc link has been used generally as shown in Fig. 5. The battery powered converter circuit coupling at inductor ($L_1$) terminal is also introduced. The chief benefit of this configuration is that the dc-dc converter does the processing of just a portion of the power generated, permitting greater efficiency in comparison with dc link coupling configuration. On similar line with this idea, an integrated power circuit is presented in this research work along with the following multiple functions: battery charge, battery regulator, and step-up or step-down conversion and load voltage regulation.

Fig. 4Proposed TPC employed B4-inverter fed PMSM motor drive system two stage conversion

As pointed out by now duty of switch ($S_1$) present in proposed converter is to extract the maximum power from PV panel using the P&O MPPT algorithm. On the contrary, the regulation of the total output voltage to the required value is the responsibility of the power sharing switch ($S_2$) present in proposed converter. In addition, when the generated energy is sufficient to drive the PMSM motor, the excess energy is utilized for charging the battery. When the power switch ($S_3$) is turned on, the inductor ($L_1$) stores the energy, and thereafter there is energy flow from the PV module to the battery. If the energy that is generated at the PV module is not adequate to drive the PMSM motor, then the power system acts as a boost converter, making the energy transfer from the battery to the PMSM motor. When the switch ($S_4$) is turned on, the inductor ($L_1$) stores the energy from the battery, and if the switch ($S_4$) is turned off, the energy that is stored in the inductor gets transferred to the PMSM motor. The command signals of the switches $S_3$ and $S_4$ are complementary. Depending on the relationship between PV generation power and load demand power, proposed standalone Multioutput buck boost converter will work in different power flow modes such as battery charging domain to converter (BCDTC), PV domain (SPVD) and battery discharging domain to converter (BDDTC).

• Solar power charges the battery and drives the load using converter (BCDTC). It operates in different operation, here the four switches conduct alternately, and PV power drives the load and charges the battery.

• Solar power does not charge the battery and drives only the load using converter (SPVDTC). It operates in different operation, here the four switches conduct alternately, and PV power drives the load. At this condition the solar power is high enough to drive the load and it does not charge the battery.

• Solar power discharges the battery and drives load using converter (BDDTC). It operates in different operation, here the four switches conduct alternately, and PV power drives the load demand takes place at this situation and also it discharges the battery.

Fig. 5Proposed TPC employed B4-inverter fed PMSM motor drive system single stage conversion

3.1. Simulink circuit model of proposed enhanced circuit

Fig. 6 shows the simulation model of a proposed converter with single stage conversion circuit.

3.2. Solar PV panel

Fig. 7 shows the simulation results of solar PV panel, at 200 W/m² solar irradiation, the input voltage is 15.75 V, input current is 0.4 A, and input power is 4.5 W. At 800 W/m² solar irradiation, input voltage is 17.5 V, input current is 1.7 A and input power is 29 W.

Fig. 6Simulink circuit model of proposed enhanced circuit

3.3. Conduction of battery

The Fig. 8 shows the simulation results of the Battery, during charging the voltage is 12.2 V, current is 0.5 A and power is 7 W. During discharging, the voltage discharges to 12.1 V, current 0.6 A and power 7.8 W.

3.4. Simulation result of PMSM

The Fig. 9(a), (b) and (c) shows the simulation result of Permanent magnet synchronous motor, where the motor speed is 1200 rpm and the torque is 3 N-m.

3.5. Simulation result of PMSM stator current

The simulation result of stator current in permanent magnet synchronous motor is 4.4 A, and it is shown in Fig. 10.

Fig. 7Simulation results of solar PV panel

a) Solar Pv panel input voltage

b) Solar Pv panel input current

c) Solar Pv panel input power

d) DC-DC converter output voltage 30.7

e) DC-DC converter output current 0.55 A

f) DC-DC converter output power 17.3

Fig. 8Simulation results of the battery

a) Battery voltage. Charging voltage: 12.2 V, discharging voltage: 12.1 V

b) Battery current. Charging current: 0.5 V, discharging current: 0.6 A

c) Battery power. Charging power: 7 W, discharging power: 7.8 W

d) State of charge of battery

Fig. 9Simulation result of permanent magnet synchronous motor

a) PMSM motor speed 1200 rmp

b) PMSM motor torque 3 Nm

c) PMSM active and reactive current

4.1. Experimental setup

The above Fig. 12 shows the experimental setup of an enhanced three port converter fed permanent magnet synchronous motor.

Fig. 12Experimental setup of enhanced three port converter fed PMSM motor

4.2. Modeling of PMSM motor to develop torque and power for DC-DC converter

The PMSM voltage equation are given in Eqs. (5), (6):

The alternating flux links are Eqs. (7), (8):

Substituting Eqs. (7), (8) in (5) and (6) we get:

By using matrix for direct axis and quadrature axis we get:

The torque across PMAM motor is:

The general torque is:

The voltage and torque equation at $d$, $q$ axis of PMAM motor is:

Converting to cos power:

So above equations are used for the developed power, based on that total harmonic distortion are calculated for reducing vibrations at PMAM motor which can be applied for the industrial applications.

4.3. Total harmonic distortion

The THD is defined as the root mean square value of the total harmonics of the signal divided by the RMS value of its fundamental signal. Lower THD results in higher power factor, lower peak currents and maximum efficiency. Low THD is such an important feature in power systems. To get an equation for THD recall that the average power of the cosine at a single harmonic is given by:

where, $k=$ 1 represents the fundamental and $k$ ≥ 2 are the harmonics. Recall also that the total average power in the signal is given by the sum of the average powers at each harmonic:

As such the THD can be calculated by finding the total power in all harmonics divided by the power in the fundamental:

In reality, there is no way to measure to the infinite harmonic, so we usually truncate the THD measurement to a certain harmonic. Note also that you need the Fourier coefficients for this measurement but that the spectrum analyser provides values in dBmV. Recall that:

Because the THD is a ratio of powers it is unit-less and is expressed as a percentage. It can also be expressed in dB as:

The shunt APF is connected in the nonlinear load with the filter inductance and operates in a closed loop. The three-phase active power filter comprises of diode clamped IGBTs with diodes, a dc-bus capacitor, RL-filter, PLL with seven level inverter and switching signal generator. Fig. 13 indicates the overall voltage and current without filter. The modified p-q theory based seven level MLI output waveform is shown in Fig. 14, also THD analysis with and without filters are shown in Fig. 15 and 16.

Fig. 13Without filter: a) output voltage, b) output current

a)

b)

Fig. 14Modified p-q theory based seven level MLI output waveform

Fig. 15THD analysis of PLL logic without filter

The three phase seven level inverter has an output current THD analysis of existing PLL module as indicated in the Fig. 17.

Fig. 16Output Voltage waveform with filter

Fig. 17THD analysis of existing PLL module

Fig. 18THD analysis of signal without filter in modified p-q theory

Fig. 19Various source signal for modified p-q model

The Fast Fourier Transform (FFT) is used to measures the order of harmonics with the fundamental frequency at 50 Hz of the source current. The magnitudes of the harmonics are plotted under non-linear load condition which is illustrated in the Fig. 18. From the result, it is observed that modified p-q theory-based shunt APF is compensating the harmonics effectively. The inputs signal applied to the proposed shunt active power filter is mentioned in the Fig. 19, which is the analysis of THD without filter.

Table 3 shows the Comparison of THD analysis with and without filter for various order harmonics. From this table it is concluded that the proposed p-q theory for reducing harmonics across the circuit is more efficient and vibration across the motor gets reduced. Table 4 indicates the comparison of conventional and Proposed theory.

4.4. Experimental result of PWM pulses to ${\mathit{S}}_1$ and ${\mathit{S}}_2$

Fig. 20 indicates the waveform of PWM Pulses across the switches $S_1$ and $S_2$. These PWM pulses are generated by B4 inverter and these pulses are fed through the PMSM motor drive.

Fig. 20Waveform of PWM pulses S1 and S2

4.5. Experimental result of PWM pulses to ${\mathit{S}}_1$ and ${\mathit{S}}_4$

Fig. 21 indicates the waveform of PWM Pulses across the switches $S_1$ and $S_4$. These PWM pulses are generated by B4 inverter and these switching pulses are fed through the PMSM motor drive.

4.6. Experimental results of DC-DC converter output voltage

Fig. 22 indicates the performance of a converter during solar insolation of 800 W/m², it generates an output voltage of about 24 V and the converter works efficiently.

Fig. 21Waveform of PWM pulses to S1 and S4

Fig. 22a) Output voltage waveform of DC-DC converter experimental, b) simulation at insolation at 800 W/m2, c) output voltage at 800 W/m2 simulation and experimental bar chart

a)

b)

c)

The performance of the converter during solar insolation of 600 W/m² and it generates an output voltage of about 20 V as shown in Fig. 23.

Fig. 24 indicates the performance of the converter during solar insolation of 200 W/m², it generates the output voltage about 12 V.

Fig. 23Output voltage waveform of DC-DC converter: a) experimental, b) simulation at insolation at 600 W/m2, c) output voltage at 600 W/m2 simulation and experimental bar chart

a)

b)

c)

4.7. Experimental results of battery

4.7.1. Battery in ideal state

Fig. 25 indicates the battery is in ideal state, the voltage from DC-DC converter is 24 V. At this time the solar alone delivers voltage to the load and the converter operates efficiently and regulate the output voltage.

Fig. 24Output voltage waveform of DC-DC converter: a) experimental, b) simulation at insolation 200 W/m2, c) output voltage at 200 W/m2 simulation and experimental bar chart

a)

b)

c)

Fig. 25Output voltage waveform of battery: a) experimental, b) simulation in ideal state, c) line chart of battery discharging state

a)

b)

c)

4.7.3. Battery in discharging state

The below Fig. 27 indicates that the battery is in discharging state, the voltage from DC-DC converter is 12 V. At this time the solar delivers voltage to the load is not sufficient, so that the battery discharges –28 A to the load, according to that converter efficiently regulate the voltage.

Fig. 26a) Output voltage waveform of battery experimental, b) simulation in charging state, c) line chart of battery charging state

a)

b)

c)

Fig. 27Output voltage waveform of battery in discharging state: a) experimental, b) simulation, c) line chart

a)

b)

c)

The Performance Comparison of conventional and proposed converters with various objects are shown in Table 5.

Table 5Performance comparison of conventional and proposed converters with various objects

Substances		Various two output converters
		Converter accessible by Sathish Kumar et al. (2017) [20]	Converter accessible by Sathish Kumar et al. (2018) [21]	Proposed improved converter for the single stage system
Switch count total		2	2	2
Total number of diodes count total		2	2	2
Total number of capacitors count total		2	2	2
Total number of inductors count total		1	1	1
Total number of components count total		7	7	7
Conversion		Buck	Boost	Buck-Boost
Switching states convolution		Easy	Multifarious	Easy
Converter accessible by Sathish Kumar et al. (2017) [20]
Switching states			States of output capacitors
$S_1$	$S_2$	–	${CO}_1$	$C_{O2}$
0	0	–	Deenergize	Deenergize
1	0	–	Energize	Energize
1	0	–	Energize	Deenergize
Converter accessible by Sathish Kumar et al. (2018) [21]
Switching states			States of output capacitors
$S_1$	$S_2$	$S_3$	${CO}_1$	$C_{O2}$
0	0	0	Energize	Energize
0	1	1	Energize	Deenergize
0	0	0	Deenergize	Deenergize
1	0	1	Energize	Deenergize
1	1	0	Energize	Energize
1	0	0	Deenergize	Deenergize
Proposed TPC converter
Switching states			States of output capacitors
$S_1$	$S_2$	–	${CO}_1$	$C_{O2}$
0	1	–	Energize	Deenergize
1	0	–	Deenergize	Energize
0	0	–	Energize	Deenergize